Pneumatic tire and method for producing same

ABSTRACT

Provided is a pneumatic tire with excellent tire noise-reducing properties. The pneumatic tire includes a resonator attached to the inner periphery of the tire, the resonator including a tube with an opening, and a cavity connected to the tube.

TECHNICAL FIELD

The present invention relates to a pneumatic tire and a method forproducing the pneumatic tire.

BACKGROUND ART

Self-sealing tires with sealants applied to the inner peripheriesthereof have been known as puncture resistant pneumatic tires(hereinafter, pneumatic tires are also referred to simply as tires).Sealants automatically seal puncture holes formed in such self-sealingtires.

Several methods have been known for producing self-sealing tires,including, for example, a method that includes: adding an organicsolvent to a sealant to reduce the viscosity of the sealant so as to beeasy to handle; attaching the diluted sealant to the inner surface of atire; and removing the organic solvent from the attached dilutedsealant, and a method that includes: mixing a base agent prepared in abatch kneader with a curing agent using a static mixer or dynamic mixerto prepare a sealant; and attaching the sealant to the inner peripheryof a tire.

Tires generate various types of noise. For example, there is a problemin that tire cavity resonance occurs during running on roads. PatentLiterature 1 discloses a technique to reduce cavity resonance byattaching a sponge to the inner side of a tire innerliner with aspecific sealant.

Air column resonance in longitudinal groove patterns is also a cause ofvehicle pass-by noise. Improvement is also needed with regard to thepass-by noise because national governments have, year after year,imposed stricter regulations on the noise to preserve the livingenvironment and protect the health of the residents.

CITATION LIST Patent Literature

Patent Literature 1: JP 2013-43643 A

SUMMARY OF INVENTION Technical Problem

With regard to tire cavity resonance, however, the technique of PatentLiterature 1 which attaches a sponge with a specific sealant may causethe following phenomenon. In the process of air-sealing after a nail isused to puncture such a self-sealing tire and then removed, the sealantmay drag the sponge into the nail hole to clog the hole. Therefore, alittle under 10% to 30% of puncture holes cannot be air-sealed.

With regard to air column resonance, pass-by noise can be reduced, forexample, by reducing the longitudinal groove pattern volume. However,this results in drainage of less water on the rainy road, thereby makingit difficult to ensure safety. Other proposed methods for reducing aircolumn resonance include the use of tire patterns to form resonators, orthe use of built-in resonators in tires. However, the former method isnot considered popular due to the limited application only to some typesof commercial tires. The latter method is impractical because, in theproduction involving vulcanization in a mold, if a cavity is formed in atire, the tire cannot be removed from the mold.

The present invention aims to solve the above problems and provide atire that has excellent tire noise-reducing properties while ensuringpractical utility. The present invention also aims to provide aself-sealing tire having excellent sealing performance and excellenttire noise-reducing properties.

Solution To Problem

The present invention relates to a pneumatic tire, including at leastone resonator on an inner periphery of the tire, the resonator includinga tube with an opening, and a cavity connected to the tube.

Preferably, the inner periphery of the tire corresponds to a treadportion.

Preferably, the resonator is a Helmholtz-type resonator.

Preferably, the opening is provided to face an inside of the tire and/orto penetrate outside of the tire.

Preferably, the opening is provided to penetrate a circumferentiallongitudinal groove of the tire.

Preferably, the pneumatic tire includes the multiple resonators tuned todifferent frequencies.

Preferably, the resonators are circumferentially provided atsubstantially equally spaced intervals.

Preferably, the resonators tuned to the same frequency are providedcircumferentially symmetrically about an axis of the tire.

Preferably, the cavity of the resonator has no bottom surface, but asurface of a sealant layer is provided as a substitute for the bottomsurface, and the opening is provided to face an inside of the tire.

Preferably, the pneumatic tire includes a sealant layer located radiallyinside an innerliner, and the resonator located radially inside thesealant layer; the sealant layer is formed by continuously and spirallyapplying a generally string-shaped sealant to the inner periphery of thetire; and the resonator is attached with the sealant applied to theinner periphery of the tire.

Preferably, the sealant contains a rubber component including abutyl-based rubber, a liquid polymer, and an organic peroxide, thesealant contains 1 to 30 parts by mass of an inorganic filler relativeto 100 parts by mass of the rubber component, and the sealant layer hasa thickness of 1.0 to 10.0 mm and a width of 85% to 115% of a width of abreaker of the tire.

Preferably, the sealant layer is formed by sequentially preparing asealant by mixing raw materials including a crosslinking agent using acontinuous kneader, and sequentially applying the sealant to the innerperiphery of the tire.

Preferably, the sealant discharged from, an outlet of the continuouskneader has a temperature of 70° C. to 150° C.

The present invention also relates to a method for producing a pneumatictire, the method including the step of attaching the resonator.

Preferably, the method includes the steps of: continuously and spirallyapplying a generally string-shaped sealant to an inner periphery of avulcanized tire; and attaching the resonator after the application ofthe sealant.

Advantageous Effects of Invention

The pneumatic tire of the present invention includes a resonator on theinner periphery of the tire, and the resonator includes a tube with anopening, and a cavity connected to the tube. Such a pneumatic tire hasexcellent noise-reducing properties while ensuring practical utility.

A first pneumatic tire of the present invention including a resonatorwhose opening is provided to face the inside of the tire can reduce tirecavity resonance (road noise). Particularly in the case of a firstpneumatic tire (self-sealing tire) of the present invention whichincludes a sealant layer located radially inside an innerliner, and theresonator located radially inside the sealant layer, and in which thesealant layer is formed by continuously and spirally applying agenerally string-shaped sealant to the inner periphery of the tire, andthe resonator is attached with the sealant applied to the innerperiphery of the tire, the following advantages can be obtained: cavityresonance can be reduced, the resonator can be attached by takingadvantage of the adhesiveness of the sealant, and in spite of utilizingthe adhesiveness, the deterioration of sealing performance can beprevented so that the tire can maintain the sealing performance.Furthermore, practical utility can also be ensured.

A second pneumatic tire of the present invention including a resonatorwhose opening is provided to penetrate outside of the tire can reduceair column resonance (pattern noise) in the tire grooves. Like the firstself-sealing tire, particularly the second pneumatic tire (self-sealingtire) of the present invention which includes a resonator whose openingis provided to penetrate outside of the tire provides the followingadvantages: air column resonance can be reduced, the resonator can beclosely attached by taking advantage of the adhesiveness of the sealant,and leakage of the air in the tire through the opening can be preventeddue to the close attachment achieved by virtue of the adhesiveness,whereby the retention of the air in the tire can be maintained. It isalso possible to retain the air even upon puncture because the sealantexhibits sealing performance. Practical utility can also be ensured.

The method for producing a pneumatic tire of the present inventionincludes the step of attaching the resonator. By this method, tires withhigh tire noise-reducing properties can be stably produced with highproductivity. Particularly the method for producing a self-sealing tireincludes the steps of continuously and spirally applying a generallystring-shaped sealant to the inner periphery of a vulcanized tire; andattaching the resonator after the application of the sealant.

Such a method can stably produce, with high productivity, the firstself-sealing tire of the present invention which achieves good cavityresonance-reducing properties, adhesion of the resonator, sealingperformance (air retention properties) upon puncture, and practicalutility.

Furthermore, such a method can stably produce, with high productivity,the second self-sealing tire which achieves good air columnresonance-reducing properties, adhesion of the resonator, prevention ofleakage of the air in the tire through the opening, sealing performance(air retention properties) upon puncture, and practical utility.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view schematically showing an example of anapplicator used in a method for producing a self-sealing tire.

FIG. 2 is an enlarged view showing the vicinity of the tip of the nozzleincluded in the applicator shown in FIG. 1.

FIG. 3 is an explanatory view schematically showing the positionalrelationship of the nozzle to the tire.

FIG. 4 is an explanatory view schematically showing an example of agenerally string-shaped sealant continuously and spirally attached tothe inner periphery of the tire.

FIG. 5 are enlarged views showing the vicinity of the tip of the nozzleincluded in the applicator shown in FIG. 1.

FIG. 6 is an explanatory view schematically showing an example of asealant attached to a self-sealing tire.

FIG. 7 is an explanatory view schematically showing an example of aproduction facility used in a method for producing a self-sealing tire.

FIG. 8 is an explanatory view schematically showing an example of across section of the sealant shown in FIG. 4 when the sealant is cutalong the straight line A-A orthogonal to the direction along which thesealant is applied (longitudinal direction).

FIG. 9 is an explanatory view schematically showing an example of across section of a pneumatic tire.

FIG. 10 is an explanatory view schematically showing an example of aresonator.

FIG. 11 is an exemplary schematic view showing resonators providedradially inside in a tire.

FIG. 12 is a photograph of a resonator provided radially inside in atire.

FIG. 13 is a schematic view showing an example of a resonator providedto penetrate a circumferential longitudinal groove of a tire.

FIG. 14 is an exemplary schematic view showing longitudinal grooves andlateral grooves of a tire.

DESCRIPTION OF EMBODIMENTS

The pneumatic tire of the present invention includes a resonator on theinner periphery of the tire, and the resonator includes a tube with anopening, and a cavity connected to the tube. Such a pneumatic tire ofthe present invention can be produced by, for example, a methodincluding the step of attaching the resonator.

(First Pneumatic Tire)

The first embodiment of the pneumatic tire of the present invention maybe a first pneumatic tire which includes a resonator whose opening isprovided to face the inside of the tire. The first pneumatic tireincluding a resonator whose opening is provided to face the inside ofthe tire can reduce tire cavity resonance while preventing theabove-described phenomenon observed when a sponge is attached.Particularly in the case of a first self-sealing tire in which aresonator is attached with a sealant, cavity resonance can be reduced,the resonator can be better attached by taking advantage of theadhesiveness of the sealant, and in spite of utilizing the adhesiveness,the deterioration of sealing performance can be prevented so that thetire can maintain the sealing performance (air retention properties)upon puncture. Furthermore, good practical utility can also be obtained.

The first pneumatic tire of the present invention including a resonatorwhose opening is provided to face the inside of the tire can be producedby attaching (placing) a resonator to the inner periphery of a tire withan adhesive, a sealant, or the like while allowing the opening to facethe inside of the tire. For example, a first pneumatic tire whichincludes a resonator whose opening is provided to face the inside of thetire and does not include a sealant layer can be produced by attachingthe resonator to the inner periphery of an innerliner with an adhesiveor the like, without forming a sealant layer as described later. A firstself-sealing tire of the present invention in which a resonator whoseopening is provided to face the inside of the tire is attached with asealant applied to the inner periphery of the tire can be produced byforming a sealant layer and then attaching the resonator to the sealantlayer by taking advantage of the adhesiveness of the layer.

(Second pneumatic tire)

The second embodiment of the pneumatic tire of the present invention maybe a second pneumatic tire which includes a resonator whose opening isprovided to penetrate outside of the tire. The second pneumatic tireincluding a resonator whose opening is provided to penetrate outside ofthe tire can reduce air column resonance in the tire grooves.Particularly in the case of a second self-sealing tire in which aresonator is attached with a sealant, air column resonance can bereduced, and the resonator can be better attached by taking advantage ofthe adhesiveness of the sealant. Although the penetration outside of thetire may cause air leakage, such leakage of the air in the tire throughthe opening can also be prevented by closely attaching the resonator bytaking advantage of the adhesiveness of the sealant, whereby theretention of the air in the tire can be maintained. Furthermore, it ispossible to retain the air even upon puncture with a nail or the likebecause the sealant exhibits sealing performance. In addition, practicalutility can also be ensured.

The second pneumatic tire of the present invention including a resonatorwhose opening is provided to penetrate outside of the tire can beproduced as a self-sealing tire by attaching (placing) a resonator tothe inner periphery of a tire with a sealant while allowing the openingto penetrate outside of the tire.

The following describes methods for producing the first or secondself-sealing tire as examples of the method for producing a pneumatictire of the present invention. The exemplary methods include the stepsof: continuously and spirally applying a generally string-shaped sealantto the inner periphery of a vulcanized tire; and attaching the resonatorafter the application of the sealant.

The first or second self-sealing tire may be produced, for example, bypreparing a sealant by mixing the components of the sealant, and thenattaching the sealant to the inner periphery of a tire by application orother means to form a sealant layer. The self-sealing tire includes thesealant layer located radially inside an innerliner.

The hardness (viscosity) of the sealant needs to be adjusted to anappropriate viscosity according to the service temperature bycontrolling the rubber component and the degree of crosslinking. Therubber component is controlled by varying the type and amount of liquidrubber, plasticizers, or carbon black, while the degree of crosslinkingis controlled by varying the type and amount of crosslinking agents orcrosslinking activators.

Any sealant that shows adhesion may be used, and rubber compositionsconventionally used to seal punctures of tires can be used. The rubbercomponent constituting a main ingredient of such a rubber compositionmay include a butyl-based rubber. Examples of the butyl-based rubberinclude butyl rubber (IIR) and halogenated butyl rubbers (X-IIR) such asbrominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR).In particular, in view of fluidity and other properties, either or bothof butyl rubber and halogenated butyl rubbers can be suitably used. Thebutyl-based rubber to be used is preferably in the form of pellets. Sucha pelletized butyl-based rubber can be precisely and suitably suppliedto a continuous kneader so that the sealant can be produced with highproductivity.

To reduce the deterioration of the fluidity of the sealant, thebutyl-based rubber to be used is preferably a butyl-based rubber Ahaving a Mooney viscosity ML₁₊₈ at 125° C. of at least 20 but less than40 and/or a butyl-based rubber B having a Mooney viscosity ML₁₊₈ at 125°C. of at least 40 but not more than 80. It is particularly suitable touse at least the butyl-based rubber A. When the butyl-based rubbers Aand B are used in combination, the blending ratio may be appropriatelychosen.

The Mooney viscosity ML₁₊₈ at 125° C. of the butyl-based rubber A ismore preferably 25 or more, still more preferably 28 or more, but morepreferably 38 or less, still more preferably 35 or less. If the Mooneyviscosity is less than 20, the fluidity may be reduced. If the Mooneyviscosity is 40 or more, the effect of the combined use may not beachieved.

The Mooney viscosity ML₁₊₈ at 125° C. of the butyl-based rubber B ismore preferably 45 or more, still more preferably 48 or more, but morepreferably 70 or less, still more preferably 60 or less. If the Mooneyviscosity is less than 40, the effect of the combined use may not beachieved. If the Mooney viscosity is more than 80, sealing performancemay be reduced.

The Mooney viscosity ML₁₊₈ at 125° C. is determined in conformity withJIS K-6300-1:2001 at a test temperature of 125° C. using an L type rotorwith a preheating time of one minute and a rotation time of eightminutes.

The rubber component may be a combination with other ingredients such asdiene rubbers, including natural rubber (NR), polyisoprene rubber (IR),polybutadiene rubber (BR), styrene-butadiene rubber (SBR),styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-dienerubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber(NBR), and butyl rubber (IIR). In view of fluidity and other properties,the amount of the butyl-based rubber based on 100% by mass of the rubbercomponent is preferably 90% by mass or more, more preferably 95% by massor more, particularly preferably 100% by mass.

Examples of the liquid polymer used in the sealant include liquidpolybutene, liquid polyisobutene, liquid polyisoprene, liquidpolybutadiene, liquid poly-α-olefin, liquid isobutylene, liquidethylene-α-olefin copolymers, liquid ethylene-propylene copolymers, andliquid ethylene-butylene copolymers. To provide adhesion and otherproperties, liquid polybutene is preferred among these. Examples of theliquid polybutene include copolymers having a long-chain hydrocarbonmolecular structure which is based on isobutene and further reacted withnormal butene. Hydrogenated liquid polybutene may also be used.

To prevent the sealant from flowing during high-speed running, theliquid polymer (e.g. liquid polybutene) to be used is preferably aliquid polymer A having a kinematic viscosity at 100° C. of 550 to 625mm²/s and/or a liquid polymer B having a kinematic viscosity at 100° C.of 3,540 to 4,010 mm²/s, more preferably a combination of the liquidpolymers A and B.

The kinematic viscosity at 100° C. of the liquid polymer A (e.g. liquidpolybutene) is preferably 550 mm²/s or higher, more preferably 570 mm²/sor higher. If the kinematic viscosity is lower than 550 mm²/s, flowingof the sealant may occur. The kinematic viscosity at 100° C. ispreferably 625 mm²/s or lower, more preferably 610 mm²/s or lower. Ifthe kinematic viscosity is higher than 625 mm²/s, the sealant may havehigher viscosity and deteriorated extrudability.

The kinematic viscosity at 100° C. of the liquid polymer B (e.g. liquidpolybutene) is preferably 3,600 mm²/s or higher, more preferably 3,650mm²/s or higher. If the kinematic viscosity is lower than 3,540 mm²/s,the sealant may have too low a viscosity and easily flow during serviceof the tire, resulting in deterioration of sealing performance oruniformity.

The kinematic viscosity at 100° C. is preferably 3, 900 mm²/s or lower,more preferably 3,800 mm²/s or lower. If the kinematic viscosity ishigher than 4,010 mm²/s, sealing performance may deteriorate.

The kinematic viscosity at 40° C. of the liquid polymer A (e.g. liquidpolybutene) is preferably 20,000 mm²/s or higher, more preferably 23,000mm²/s or higher. If the kinematic viscosity is lower than 20,000 mm²/s,the sealant may be soft so that its flowing can occur. The kinematicviscosity at 40° C. is preferably 30,000 mm²/s or lower, more preferably28,000 mm²/s or lower. If the kinematic viscosity is higher than 30,000mm²/s, the sealant may have too high a viscosity and deterioratedsealing performance.

The kinematic viscosity at 40° C. of the liquid polymer B (e.g. liquidpolybutene) is preferably 120,000 mm²/s or higher, more preferably150,000 mm²/s or higher. If the kinematic viscosity is lower than120,000 mm²/s, the sealant may have too low a viscosity and easily flowduring service of the tire, resulting in deterioration of sealingperformance or uniformity.

The kinematic viscosity at 40° C. is preferably 200,000 mm²/s or lower,more preferably 170,000 mm²/s or lower. If the kinematic viscosity ishigher than 200,000 mm²/s, the sealant may have too high a viscosity anddeteriorated sealing performance.

The kinematic viscosity is determined in conformity with JIS K 2283-2000at 100° C. or 40° C.

The amount of the liquid polymer (the combined amount of the liquidpolymers A and B and other liquid polymers) relative to 100 parts bymass of the rubber component is preferably 50 parts by mass or more,more preferably 100 parts by mass or more, still more preferably 150parts by mass or more. If the amount is less than 50 parts by mass,adhesion may be reduced. The amount is preferably 400 parts by mass orless, more preferably 300 parts by mass or less, still more preferably250 parts by mass or less. If the amount is more than 400 parts by mass,flowing of the sealant may occur.

In the case where the liquid polymers A and B are used in combination,the blending ratio of these polymers [(amount of liquid polymerA)/(amount of liquid polymer B)] is preferably 10/90 to 90/10, morepreferably 30/70 to 70/30, still more preferably 40/60 to 60/40. Whenthe blending ratio is within the range indicated above, the sealant isprovided with good adhesion.

The organic peroxide (crosslinking agent) is not particularly limited,and conventionally known compounds can be used. The use of a butyl-basedrubber and a liquid polymer in an organic peroxide crosslinking systemimproves adhesion, sealing performance, fluidity, and processability.

Examples of the organic peroxide include acyl peroxides such as benzoylperoxide, dibenzoyl peroxide, and p-chlorobenzoyl peroxide; peroxyesterssuch as 1-butyl peroxyacetate, t-butyl peroxybenzoate, and t-butylperoxyphthalate; ketone peroxides such as methyl ethyl ketone peroxide;alkyl peroxides such as di-t-butylperoxybenzoate and1,3-bis(1-butylperoxyisopropyl)benzene; hydroperoxides such as t-butylhydroperoxide; and dicumyl peroxide and t-butylcumyl peroxide. In viewof adhesion and fluidity, acyl peroxides are preferred among these, withdibenzoyl peroxide being particularly preferred. Moreover, the organicperoxide (crosslinking agent) to be used is preferably in the form ofpowder or a dilution (slurry or suspension) thereof. The organicperoxide (crosslinking agent) in such a form can be precisely andsuitably supplied to a continuous kneader so that the sealant can beproduced with high productivity.

The amount of the organic peroxide (crosslinking agent) relative to 100parts by mass of the rubber component is preferably 0.5 parts by mass ormore, more preferably 1 part by mass or more, still more preferably 5parts by mass or more. If the amount is less than 0.5 parts by mass,crosslink density may decrease so that flowing of the sealant can occur.The amount is preferably 40 parts by mass or less, more preferably 20parts by mass or less, still more preferably 15 parts by mass or less.If the amount is more than 40 parts by mass, crosslink density mayincrease so that the sealant can be hardened and show reduced sealingperformance.

The crosslinking activator (vulcanization accelerator) to be used may beat least one selected from the group consisting of sulfenamidecrosslinking activators, thiazole crosslinking activators, thiuramcrosslinking activators, thiourea crosslinking activators, guanidinecrosslinking activators, dithiocarbamate crosslinking activators,aldehyde-amine crosslinking activators, aldehyde-ammonia crosslinkingactivators, imidazoline crosslinking activators, xanthate crosslinkingactivators, and quinone dioxime compounds (quinoid compounds). Forexample, quinone dioxime compounds (quinoid compounds) can be suitablyused. The use of a butyl-based rubber and a liquid polymer in acrosslinking system including a crosslinking activator added to anorganic peroxide improves adhesion, sealing performance, fluidity, andprocessability.

Examples of the quinone dioxime compound include p-benzoquinone dioxime,p-quinone dioxime, p-quinone dioxime diacetate, p-quinone dioximedicaproate, p-quinone dioxime dilaurate, p-quinone dioxime distearate,p-quinone dioxime dicrotonate, p-quinone dioxime dinaphthenate,p-quinone dioxime succinate, p-quinone dioxime adipate, p-quinonedioxime difuroate, p-quinone dioxime dibenzoate, p-quinone dioxime di(o-chlorobenzoate), p-quinone dioxime di (p-chlorobenzoate), p-quinonedioxime di (p-nitrobenzoate), p-quinone dioxime di (m-nitrobenzoate),p-quinone dioxime di (3,5-dinitrobenzoate), p-quinone dioxime di(p-methoxybenzoate), p-quinone dioxime di (n-amyloxybenzoate), andp-quinone dioxime di (m-bromobenzoate). In view of adhesion, sealingperformance, and fluidity, p-benzoquinone dioxime is preferred amongthese. Moreover, the crosslinking activator (vulcanization accelerator)to be used is preferably in the form of powder. Such a powderedcrosslinking activator (vulcanization accelerator) can be precisely andsuitably supplied to a continuous kneader so that the sealant can beproduced with high productivity.

The amount of the crosslinking activator (e.g. quinone dioximecompounds) relative to 100 parts by mass of the rubber component ispreferably 0.5 parts by mass or more, more preferably 1 part by mass ormore, still more preferably 3 parts by mass or more. If the amount isless than 0.5 parts by mass, flowing of the sealant may occur. Theamount is preferably 40 parts by mass or less, more preferably 20 partsby mass or less, still more preferably 15 parts by mass or less. If theamount is more than 40 parts by mass, sealing performance may bereduced.

The sealant may further contain an inorganic filler such as carbonblack, silica, calcium carbonate, calcium silicate, magnesium oxide,aluminum oxide, barium sulfate, talc, or mica; or a plasticizer such asaromatic process oils, naphthenic process oils, or paraffinic processoils.

The amount of the inorganic filler relative to 100 parts by mass of therubber component is preferably 1 part by mass or more, more preferably10 parts by mass or more. If the amount is less than 1 part by mass,sealing performance may be reduced due to degradation by ultravioletrays. The amount is preferably 50 parts by mass or less, more preferably40 parts by mass or less, still more preferably 30 parts by mass orless. If the amount is more than 50 parts by mass, the sealant may havetoo high a viscosity and deteriorated sealing performance.

To prevent degradation by ultraviolet rays, the inorganic filler ispreferably carbon black. In this case, the amount of the carbon blackrelative to 100 parts by mass of the rubber component is preferably 1part by mass or more, more preferably 10 parts by mass or more. If theamount is less than 1 part by mass, sealing performance may be reduceddue to degradation by ultraviolet rays. The amount is preferably 50parts by mass or less, more preferably 40 parts by mass or less, stillmore preferably 25 parts by mass or less. If the amount is more than 50parts by mass, the sealant may have too high a viscosity anddeteriorated sealing performance.

The amount of the plasticizer relative to 100 parts by mass of therubber component is preferably 1 part by mass or more, more preferably 5parts by mass or more. If the amount is less than 1 part by mass, thesealant may show lower adhesion to tires, failing to have sufficientsealing performance. The amount is preferably 40 parts by mass or less,more preferably 20 parts by mass or less. If the amount is more than 40parts by mass, the sealant may slide in the kneader so that it cannot beeasily kneaded.

The sealant is preferably prepared by mixing a pelletized butyl-basedrubber, a powdered crosslinking agent, and a powdered crosslinkingactivator, and more preferably by mixing a pelletized butyl-basedrubber, a liquid polybutene, a plasticizer, carbon black powder, apowdered crosslinking agent, and a powdered crosslinking activator. Suchraw materials can be suitably supplied to a continuous kneader so thatthe sealant can be produced with high productivity.

The sealant is preferably obtained by incorporating a rubber componentincluding butyl rubber with predetermined amounts of a liquid polymer,an organic peroxide, and a crosslinking activator.

A sealant obtained by incorporating butyl rubber with a liquid polymersuch as liquid polybutene, especially wherein the butyl rubber and theliquid polymer are each a combination of two or more materials havingdifferent viscosities, can achieve a balanced improvement in adhesion,sealing performance, fluidity, and processability. This is because theintroduction of a liquid polymer component to an organic peroxidecrosslinking system using butyl rubber as the rubber component providesadhesion, and especially the use of liquid polymers or solid butylrubbers having different viscosities reduces flowing of the sealantduring high-speed running. Therefore, the sealant can achieve a balancedimprovement in adhesion, sealing performance, fluidity, andprocessability.

The viscosity at 40° C. of the sealant is not particularly limited. Inorder to allow the sealant to suitably maintain a generally string shapewhen it is applied to the inner periphery of a tire, and in view ofadhesion, fluidity, and other properties, the viscosity at 40° C. ispreferably 3,000 Pa·s or higher, more preferably 5,000 Pa·s or higher,but preferably 70,000 Pa·s or lower, more preferably 50,000 Pa·s orlower. If the viscosity is lower than 3,000 Pa·s, the applied sealantmay flow when the tire stops rotating, so that the sealant cannotmaintain the film thickness. Also, if the viscosity is higher than70,000 Pa·s, the sealant cannot be easily discharged from the nozzle.

The viscosity of the sealant is determined at 40° C. in conformity withJIS K 6833 using a rotational viscometer.

A self-sealing tire including a sealant layer located radially inside aninnerliner can be produced by preparing a sealant by mixing theaforementioned materials, and applying the sealant to the innerperiphery of a tire, and preferably to a radially inner side of aninnerliner. The materials of the sealant may be mixed using knowncontinuous kneaders, for example. In particular, they are preferablymixed using a co-rotating or counter-rotating multi-screw kneadingextruder, and especially a twin screw kneading extruder.

The continuous kneader (especially twin screw kneading extruder)preferably has a plurality of supply ports for supplying raw materials,more preferably at least three supply ports, still more preferably atleast three supply ports including upstream, midstream, and downstreamsupply ports. By sequentially supplying the raw materials to thecontinuous kneader (especially twin screw kneading extruder), the rawmaterials are mixed and sequentially and continuously prepared into asealant.

Preferably, the raw materials are sequentially supplied to thecontinuous kneader (especially twin screw kneading extruder), startingfrom the material having a higher viscosity. In this case, the materialscan be sufficiently mixed and prepared into a sealant of a consistentquality. Moreover, powder materials, which improve kneadability, shouldbe introduced as upstream as possible.

The organic peroxide is preferably supplied to the continuous kneader(especially twin screw kneading extruder) through its downstream supplyport. In this case, the time period from supplying the organic peroxideto applying the sealant to a tire can be shortened so that the sealantcan be applied to a tire before it is cured. This allows for more stableproduction of self-sealing tires.

Since kneading is unsuccessfully accomplished when a large amount of theliquid polymer is introduced at once into the continuous kneader(especially twin screw kneading extruder), the liquid polymer ispreferably supplied to the continuous kneader (especially twin screwkneading extruder) through a plurality of supply ports. In this case,the sealant can be more suitably kneaded.

When a continuous kneader (especially twin screw kneading extruder) isused, the sealant is preferably prepared using the continuous kneader(especially twin screw kneading extruder) having at least three supplyports by supplying a rubber component such as a butyl-based rubber, aninorganic filler, and a crosslinking activator each from the upstreamsupply port, a liquid polymer B from the midstream supply port, and aliquid polymer A, an organic peroxide, and a plasticizer each from thedownstream supply port of the continuous kneader (especially twin screwkneading extruder), followed by kneading and extrusion. The materialssuch as liquid polymers may be entirely or partially supplied from therespective supply ports. Preferably, 95% by mass or more of the totalamount of each material is supplied from the supply port.

Preferably, all the raw materials to be introduced into the continuouskneader are introduced into the continuous kneader under the control ofa quantitative feeder. This allows for continuous and automatedpreparation of the sealant.

Any feeder that can provide quantitative feeding may be used, includingknown feeders such as screw feeders, plunger pumps, gear pumps, mohnopumps, tube pumps, or diaphragm pumps.

Solid raw materials (especially pellets or powder) such as pelletizedbutyl-based rubbers, carbon black powder, powdered crosslinking agents,and powdered crosslinking activators are preferably quantitativelysupplied using a screw feeder. This allows the solid raw materials to besupplied precisely in fixed amounts, thereby allowing for the productionof a higher quality sealant and therefore a higher quality self-sealingtire.

Moreover, the solid raw materials are preferably individually suppliedthrough separate respective feeders. In this case, the raw materialsneed not to be blended beforehand, which facilitates supply of thematerials in the mass production.

The plasticizer is preferably quantitatively supplied using a plungerpump. This allows the plasticizer to be supplied precisely in a fixedamount, thereby allowing for the production of a higher quality sealantand therefore a higher quality self-sealing tire.

The liquid polymer is preferably quantitatively supplied using a gearpump. This allows the liquid polymer to be supplied precisely in a fixedamount, thereby allowing for the production of a higher quality sealantand therefore a higher quality self-sealing tire.

The liquid polymer to be supplied is preferably kept under constanttemperature control. The constant temperature control allows the liquidpolymer to be supplied more precisely in a fixed amount. The liquidpolymer to be supplied preferably has a temperature of 20° C. to 90° C.,more preferably 40° C. to 70° C.

In view of easy mixing and extrudability, the mixing in the continuouskneader (especially twin screw kneading extruder) is preferably carriedout at a barrel temperature of 30° C. (preferably 50° C.) to 150° C.

In view of sufficient mixing, preferably, the materials suppliedupstream are mixed for 1 to 3 minutes, and the materials suppliedmidstream are mixed for 1 to 3 minutes, while the materials supplieddownstream are preferably mixed for 0.5 to 2 minutes in order to avoidcrosslinking. The times for mixing the materials each refer to theresidence time in the continuous kneader (especially twin screw kneadingextruder) from supply to discharge. For example, the time for mixing thematerials supplied downstream means the residence time from when theyare supplied through a downstream supply port until they are discharged.

By varying the screw rotational speed of the continuous kneader(especially twin screw kneading extruder) or the setting of atemperature controller, it is possible to control the temperature of thesealant discharged from the outlet and therefore the rate of curingacceleration of the sealant. As the screw rotational speed of thecontinuous kneader (especially twin screw kneading extruder) increases,kneadability and material temperature increase. The screw rotationalspeed does not affect the discharge amount. In view of sufficient mixingand control of the rate of curing acceleration, the screw rotationalspeed is preferably 50 to 700 (preferably 550) rpm.

In view of sufficient mixing and control of the rate of curingacceleration, the temperature of the sealant discharged from the outletof the continuous kneader (especially twin screw kneading extruder) ispreferably 70° C. to 150° C., more preferably 90° C. to 130° C. When thetemperature of the sealant is within the range indicated above, thecrosslinking reaction begins upon the application of the sealant and thesealant adheres well to the inner periphery of a tire and, at the sametime, the crosslinking reaction more suitably proceeds, whereby aself-sealing tire having high sealing performance can be produced.Moreover, the crosslinking step described later is not required in thiscase.

The amount of the sealant discharged from the outlet of the continuouskneader (especially twin screw kneading extruder) is determinedaccording to the amounts of the raw materials supplied to the supplyports. The amounts of the raw materials supplied to the supply ports arenot particularly limited, and a person skilled in the art canappropriately select the amounts. To suitably produce a self-sealingtire having much better uniformity and sealing performance, preferably asubstantially constant amount (discharge amount) of the sealant isdischarged from the outlet.

Herein, the substantially constant discharge amount means that thedischarge amount varies within a range of 93% to 107%, preferably 97% to103%, more preferably 98% to 102%, still more preferably 99% to 101%.

The outlet of the continuous kneader (especially twin screw kneadingextruder) is preferably connected to a nozzle. Since the continuouskneader (especially twin screw kneading extruder) can discharge thematerials at a high pressure, the prepared sealant can be attached in athin, generally string shape (bead shape) to a tire by means of a nozzle(preferably a small diameter nozzle creating high resistance) mounted onthe outlet. Specifically, by discharging the sealant from a nozzleconnected to the outlet of the continuous kneader (especially twin screwkneading extruder) to sequentially apply it to the inner periphery of atire, the applied sealant has a substantially constant thickness,thereby preventing deterioration of tire uniformity. This allows for theproduction of a self-sealing tire that is excellent in weight balance.

Next, for example, the mixed sealant is discharged from the nozzleconnected to the outlet of the extruder such as a continuous kneader(especially twin screw kneading extruder) to feed and apply the sealantdirectly to the inner periphery of a vulcanized tire, whereby aself-sealing tire can be produced. In this case, since the sealant whichhas been mixed in, for example, a twin screw kneading extruder and inwhich the crosslinking reaction in the extruder is suppressed isdirectly applied to the tire inner periphery, the crosslinking reactionof the sealant begins upon the application and the sealant adheres wellto the tire inner periphery and, at the same time, the crosslinkingreaction suitably proceeds. For this reason, the sealant applied to thetire inner periphery forms a sealant layer while suitably maintaining agenerally string shape. Accordingly, the sealant can be applied andprocessed in a series of steps and therefore productivity is furtherimproved. Moreover, the application of the sealant to the innerperiphery of a vulcanized tire further enhances the productivity ofself-sealing tires. Furthermore, the sealant discharged from the nozzleconnected to the outlet of the continuous kneader (especially twin screwkneading extruder) is preferably sequentially applied directly to theinner periphery of a tire. In this case, since the sealant in which thecrosslinking reaction in the continuous kneader (especially twin screwkneading extruder) is suppressed is directly and continuously applied tothe tire inner periphery, the crosslinking reaction of the sealantbegins upon the application and the sealant adheres well to the tireinner periphery and, at the same time, the crosslinking reactionsuitably proceeds, whereby a self-sealing tire that is excellent inweight balance can be produced with higher productivity.

With regard to the application of the sealant to the inner periphery ofa tire, the sealant maybe applied at least to the inner periphery of atire that corresponds to a tread portion, and more preferably at leastto the inner periphery of a tire that corresponds to a breaker. Omittingthe application of the sealant to areas where the sealant is unnecessaryfurther enhances the productivity of self-sealing tires.

The inner periphery of a tire that corresponds to a tread portion refersto a portion of the inner periphery of a tire that is located radiallyinside a tread portion which contacts the road surface. The innerperiphery of a tire that corresponds to a breaker refers to a portion ofthe inner periphery of a tire that is located radially inside a breaker.The breaker refers to a component placed inside a tread and radiallyoutside a carcass. Specifically, it is a component shown as a breaker 16in FIG. 9, for example.

Unvulcanized tires are usually vulcanized using bladders.

During the vulcanization, such a bladder inflates and closely attachesto the inner periphery (innerliner) of the tire. Hence, a mold releaseagent is usually applied to the inner periphery (innerliner) of the tireto avoid adhesion between the bladder and the inner periphery(innerliner) of the tire after completion of the vulcanization.

The mold release agent is usually a water-soluble paint or amold-releasing rubber. However, the presence of the mold release agenton the inner periphery of the tire may impair the adhesion between thesealant and the inner periphery of the tire. For this reason, it ispreferred to preliminarily remove the mold release agent from the innerperiphery of the tire. In particular, the mold release agent is morepreferably preliminarily removed at least from a portion of the tireinner periphery in which application of the sealant starts. Still morepreferably, the mold release agent is preliminarily removed from theentire area of the tire inner periphery where the sealant is to beapplied. In this case, the sealant adheres better to the tire innerperiphery and therefore a self-sealing tire having higher sealingperformance can be produced.

The mold release agent may be removed from the tire inner periphery byany method, including known methods such as buffing treatment, lasertreatment, high pressure water washing, and removal with detergents andpreferably with neutral detergents.

An example of a production facility used in the method for producing aself-sealing tire will be briefly described below referring to FIG. 7.

The production facility includes a twin screw kneading extruder 60, amaterial feeder 62 for supplying raw materials to the twin screwkneading extruder 60, and a rotary drive device 50 which fixes androtates a tire 10 while moving the tire in the width and radialdirections of the tire. The twin screw kneading extruder 60 has fivesupply ports 61, specifically, including three upstream supply ports 61a, one midstream supply port 61 b, and one downstream supply port 61 c.Further, the outlet of the twin screw kneading extruder 60 is connectedto a nozzle 30.

The raw materials are sequentially supplied from the material feeder 62to the twin screw kneading extruder 60 through the supply ports 61 ofthe twin screw kneading extruder 60 and then kneaded in the twin screwkneading extruder 60 to sequentially prepare a sealant. The preparedsealant is continuously discharged from the nozzle 30 connected to theoutlet of the twin screw kneading extruder 60. The tire is traversedand/or moved up and down (moved in the width direction and/or the radialdirection of the tire) while being rotated by the tire drive device, andthe sealant discharged from the nozzle 30 is sequentially applieddirectly to the inner periphery of the tire, whereby the sealant can becontinuously and spirally attached to the tire inner periphery. In otherwords, the sealant can be continuously and spirally attached to theinner periphery of a tire by sequentially applying the sealantcontinuously discharged from the continuous kneader (especially twinscrew kneading extruder) directly to the inner periphery of the tirewhile rotating the tire and simultaneously moving it in the widthdirection and/or the radial direction of the tire.

Such a continuous and spiral attachment of the sealant to the tire innerperiphery can prevent deterioration of tire uniformity, thereby allowingfor the production of a self-sealing tire that is excellent in weightbalance. Moreover, the continuous and spiral attachment of the sealantto the tire inner periphery allows for the formation of a sealant layerin which the sealant is uniformly provided in the circumferential andwidth directions of the tire, and especially in the circumferentialdirection of the tire. This allows for stable production of self-sealingtires having excellent sealing performance with high productivity. Thesealant is preferably attached without overlapping in the widthdirection and more preferably without gaps. In this case, thedeterioration of tire uniformity can be further prevented and a moreuniform sealant layer can be formed.

The raw materials are sequentially supplied to a continuous kneader(especially twin screw kneading extruder) which sequentially prepares asealant. The prepared sealant is continuously discharged from a nozzleconnected to the outlet of the continuous kneader (especially twin screwkneading extruder), and the discharged sealant is sequentially applieddirectly to the inner periphery of a tire. In this manner, self-sealingtires can be produced with high productivity.

The sealant layer is preferably formed by continuously and spirallyapplying a generally string-shaped sealant to the inner periphery of atire. In this case, a sealant layer formed of a generally string-shapedsealant provided continuously and spirally along the inner periphery ofa tire can be formed on the inner periphery of the tire. The sealantlayer may be formed of layers of the sealant, but preferably consists ofone layer of the sealant.

In the case of a generally string-shaped sealant, a sealant layerconsisting of one layer of the sealant can be formed by continuously andspirally applying the sealant to the inner periphery of a tire. In thecase of a generally string-shaped sealant, since the applied sealant hasa certain thickness, even a sealant layer consisting of one layer of thesealant can prevent deterioration of tire uniformity and allows for theproduction of a self-sealing tire having an excellent weight balance andgood sealing performance. Moreover, since it is sufficient to only applyone layer of the sealant without stacking layers of the sealant,self-sealing tires can be produced with higher productivity.

The number of turns of the sealant around the inner periphery of thetire is preferably 20 to 70, more preferably 20 to 60, still morepreferably 35 to 50, because then the deterioration of tire uniformitycan be prevented and a self-sealing tire having an excellent weightbalance and good sealing performance can be produced with higherproductivity. Here, two turns means that the sealant is applied suchthat it makes two laps around the inner periphery of the tire. In FIG.4, the number of turns of the sealant is six.

The use of a continuous kneader (especially twin screw kneadingextruder) enables the preparation (kneading) of a sealant and thedischarge (application) of the sealant to be simultaneously andcontinuously performed. Thus, a highly viscous and adhesive sealantwhich is difficult to handle can be directly applied to the innerperiphery of a tire without handling it, so that a self-sealing tire canbe produced with high productivity. If a sealant is prepared by kneadingwith a curing agent in a batch kneader, the time period from preparing asealant to attaching the sealant to a tire is not constant. In contrast,by sequentially preparing a sealant by mixing raw materials including anorganic peroxide using a continuous kneader (especially twin screwkneading extruder), and sequentially applying the sealant to the innerperiphery of a tire, the time period from preparing a sealant toattaching the sealant to a tire is held constant. Accordingly, when thesealant is applied through a nozzle, the amount of the sealantdischarged from the nozzle is stable; furthermore, the sealant showsconsistent adhesion while reducing the deterioration of adhesion to thetire, and even a highly viscous and adhesive sealant which is difficultto handle can be precisely applied to the tire inner periphery.Therefore, self-sealing tires of a consistent quality can be stablyproduced.

The following describes methods for applying the sealant to the innerperiphery of a tire.

First Embodiment

According to a first embodiment, a self-sealing tire can be produced,for example, by performing the Steps (1), (2), and (3) below in theprocess of applying an adhesive sealant through a nozzle to the innerperiphery of a tire while rotating the tire and simultaneously moving atleast one of the tire and nozzle in the width direction of the tire:Step (1) of measuring the distance between the inner periphery of thetire and the tip of the nozzle using a non-contact displacement sensor;Step (2) of moving at least one of the tire and nozzle in the radialdirection of the tire according to the measurement to adjust thedistance between the inner periphery of the tire and the tip of thenozzle to a predetermined length; and Step (3) of applying the sealantto the inner periphery of the tire after the distance is adjusted.

The distance between the inner periphery of the tire and the tip of thenozzle can be maintained at a constant length by measuring the distancebetween the inner periphery of the tire and the tip of the nozzle usinga non-contact displacement sensor and feeding back the measurement.Moreover, since the sealant is applied to the tire inner periphery whilemaintaining the distance at a constant length, the sealant can have auniform thickness without being affected by variations in tire shape andirregularities at joint portions or the like. Furthermore, since it isnot necessary to enter the coordinate data of each tire having adifferent size as in the conventional art, the sealant can beefficiently applied.

FIG. 1 is an explanatory view schematically showing an example of anapplicator used in a method for producing a self-sealing tire, and FIG.2 is an enlarged view showing the vicinity of the tip of the nozzleincluded in the applicator shown in FIG. 1.

FIG. 1 shows a cross section of a part of a tire 10 in the meridionaldirection (a cross section taken along a plane including the width andradial directions of the tire). FIG. 2 shows a cross section of a partof the tire 10 taken along a plane including the circumferential andradial directions of the tire. In FIGS. 1 and 2, the width direction(axis direction) of the tire is indicated by an arrow X, thecircumferential direction of the tire is indicated by an arrow Y, andthe radial direction of the tire is indicated by an arrow Z.

The tire 10 is mounted on a rotary drive device (not shown) which fixesand rotates a tire while moving the tire in the width and radialdirections of the tire. The rotary drive device allows for the followingindependent operations: rotation around the axis of the tire, movementin the width direction of the tire, and movement in the radial directionof the tire.

The rotary drive device includes a controller (not shown) capable ofcontrolling the amount of movement in the radial direction of the tire.The controller may be capable of controlling the amount of movement inthe tire width direction and/or the rotational speed of the tire.

A nozzle 30 is attached to the tip of an extruder (not shown) and can beinserted into the inside of the tire 10. Then an adhesive sealant 20extruded from the extruder is discharged from the tip 31 of the nozzle30.

A non-contact displacement sensor 40 is attached to the nozzle 30 tomeasure the distance d between the inner periphery 11 of the tire 10 andthe tip 31 of the nozzle 30.

Thus, the distance d to be measured by the non-contact displacementsensor is the distance in the radial direction of the tire between theinner periphery of the tire and the tip of the nozzle.

According to the method for producing a self-sealing tire of thisembodiment, the tire 10 formed through a vulcanization step is firstmounted on the rotary drive device, and the nozzle 30 is inserted intothe inside of the tire 10. Then, as shown in FIGS. 1 and 2, the tire 10is rotated and simultaneously moved in the width direction while thesealant 20 is discharged from the nozzle 30, whereby the sealant iscontinuously applied to the inner periphery 11 of the tire 10. The tire10 is moved in the width direction according to the pre-entered profileof the inner periphery 11 of the tire 10.

The sealant 20 preferably has a generally string shape as describedlater. More specifically, the sealant preferably maintains a generallystring shape when the sealant is applied to the inner periphery of thetire. In this case, the generally string-shaped sealant 20 iscontinuously and spirally attached to the inner periphery 11 of the tire10.

The generally string shape as used herein refers to a shape having acertain width, a certain thickness, and a length longer than the width.FIG. 4 schematically shows an example of a generally string-shapedsealant continuously and spirally attached to the inner periphery of atire, and FIG. 8 schematically shows an example of a cross section ofthe sealant shown in FIG. 4 when the sealant is cut along the straightline A-A orthogonal to the direction along which the sealant is applied(longitudinal direction). Thus, the generally string-shaped sealant hasa certain width (length indicated by W in FIG. 8) and a certainthickness (length indicated by D in FIG. 8). The width of the sealantmeans the width of the applied sealant. The thickness of the sealantmeans the thickness of the applied sealant, more specifically thethickness of the sealant layer.

Specifically, the generally string-shaped sealant is a sealant having athickness (thickness of the applied sealant or the sealant layer, lengthindicated by D in FIG. 8) satisfying a preferable numerical range and awidth (width of the applied sealant, length indicated by W in FIG. 4 orW₀ in FIG. 6) satisfying a preferable numerical range as describedlater, and more preferably a sealant having a ratio of the thickness tothe width of the sealant [(thickness of sealant)/(width of sealant)]satisfying a preferable numerical range as described later. Thegenerally string-shaped sealant is also a sealant having across-sectional area satisfying a preferable numerical range asdescribed later.

According to the method for producing a self-sealing tire of thisembodiment, the sealant is applied to the inner periphery of a tire bythe following Steps (1) to (3).

<Step (1)>

As shown in FIG. 2, the distance d between the inner periphery 11 of thetire 10 and the tip 31 of the nozzle 30 is measured with the non-contactdisplacement sensor 40 before the application of the sealant 20. Thedistance d is measured for every tire 10 to whose inner periphery 11 isapplied the sealant 20, from the start to the end of application of thesealant 20.

<Step (2)>

The distance d data is transmitted to the controller of the rotary drivedevice. According to the data, the controller controls the amount ofmovement in the radial direction of the tire so that the distancebetween the inner periphery 11 of the tire 10 and the tip 31 of thenozzle 30 is adjusted to a predetermined length.

<Step (3)>

Since the sealant 20 is continuously discharged from the tip 31 of thenozzle 30, it is applied to the inner periphery 11 of the tire 10 afterthe above distance is adjusted. Through the above Steps (1) to (3), thesealant 20 having a uniform thickness can be applied to the innerperiphery 11 of the tire 10.

FIG. 3 is an explanatory view schematically showing the positionalrelationship of the nozzle to the tire.

As shown in FIG. 3, the sealant can be applied while maintaining thedistance between the inner periphery 11 of the tire 10 and the tip 31 ofthe nozzle 30 at a predetermined distance d₀ during the movement of thenozzle 30 to positions (a) to (d) relative to the tire 10.

To provide more suitable effects, the controlled distance d₀ ispreferably 0.3 mm or more, more preferably 1.0 mm or more. If thedistance is less than 0.3 mm, the tip of the nozzle is too close to theinner periphery of the tire, which makes it difficult to allow theapplied sealant to have a predetermined thickness. The controlleddistance d₀ is also preferably 3.0 mm or less, more preferably 2.0 mm orless. If the distance is more than 3.0 mm, the sealant may not beattached well to the tire, thereby resulting in reduced productionefficiency.

The controlled distance d₀ refers to the distance in the radialdirection of the tire between the inner periphery of the tire and thetip of the nozzle after the distance is controlled in Step (2).

To provide more suitable effects, the controlled distance d₀ ispreferably 30% or less, more preferably 20% or less of the thickness ofthe applied sealant. The controlled distance do is also preferably 5% ormore, more preferably 10% or more of the thickness of the appliedsealant.

The thickness of the sealant (thickness of the applied sealant or thesealant layer, length indicated by D in FIG. 8) is not particularlylimited. To provide more suitable effects, the thickness of the sealantis preferably 1.0 mm or more, more preferably 1.5 mm or more, still morepreferably 2.0 mm or more, particularly preferably 2.5 mm or more. Also,the thickness of the sealant is preferably 10 mm or less, morepreferably 8.0 mm or less, still more preferably 5.0 mm or less. If thethickness is less than 1.0 mm, then a puncture hole formed in the tireis difficult to reliably seal. Also, a thickness of more than 10 mm isnot preferred because tire weight increases, although with littleimprovement in the effect of sealing puncture holes. The thickness ofthe sealant can be controlled by varying the rotational speed of thetire, the velocity of movement in the tire width direction, the distancebetween the tip of the nozzle and the inner periphery of the tire, orother factors.

The sealant preferably has a substantially constant thickness (thicknessof the applied sealant or the sealant layer). In this case, thedeterioration of tire uniformity can be further prevented and aself-sealing tire having much better weight balance can be produced.

The substantially constant thickness as used herein means that thethickness varies within a range of 90% to 110%, preferably 95% to 105%,more preferably 98% to 102%, still more preferably 99% to 101%.

To reduce clogging of the nozzle so that excellent operational stabilitycan be obtained and to provide more suitable effects, a generallystring-shaped sealant is preferably used and more preferably spirallyattached to the inner periphery of the tire. However, a sealant nothaving a generally string shape may also be used and applied by sprayingonto the tire inner periphery.

In the case of a generally string-shaped sealant, the width of thesealant (width of the applied sealant, length indicated by W in FIG. 4)is not particularly limited. To provide more suitable effects, the widthof the sealant is preferably 0.8 mm or more, more preferably 1.3 mm ormore, still more preferably 1.5 mm or more. If the width is less than0.8 mm, the number of turns of the sealant around the tire innerperiphery may increase, reducing production efficiency. The width of thesealant is also preferably 18 mm or less, more preferably 13 mm or less,still more preferably 9.0 mm or less, particularly preferably 7.0 mm orless, most preferably 6.0 mm or less, still most preferably 5.0 mm orless. If the width is more than 18 mm, a weight imbalance may be morelikely to occur.

The ratio of the thickness of the sealant (thickness of the appliedsealant or the sealant layer, length indicated by D in FIG. 8) to thewidth of the sealant (width of the applied sealant, length indicated byW in FIG. 4) [(thickness of sealant)/(width of sealant)] is preferably0.6 to 1.4, more preferably 0.7 to 1.3, still more preferably 0.8 to1.2, particularly preferably 0.9 to 1.1. A ratio closer to 1.0 resultsin a sealant having an ideal string shape, so that a self-sealing tirehaving high sealing performance can be produced with higherproductivity.

To provide more suitable effects, the cross-sectional area of thesealant (cross-sectional area of the applied sealant, area calculated byD×W in FIG. 8) is preferably 0.8 mm² or more, more preferably 1.95 mm²or more, still more preferably 3.0 mm² or more, particularly preferably3.75 mm² or more, but preferably 180 mm² or less, more preferably 104mm² or less, still more preferably 45 mm² or less, particularlypreferably 35 mm² or less, most preferably 25 mm² or less.

The width of the area where the sealant is attached (hereinafter alsoreferred to as the width of the attachment area or the width of thesealant layer, and corresponding to a length equal to 6×W in FIG. 4 or alength equal to W₁+6×W₀ in FIG. 6) is not particularly limited. Toprovide more suitable effects, the width is preferably 80% or more, morepreferably 90% or more, still more preferably 100% or more, butpreferably 120% or less, more preferably 110% or less, of the treadcontact width.

To provide more suitable effects, the width of the sealant layer ispreferably 85% to 115%, more preferably 95% to 105% of the width of thebreaker of the tire (the length of the breaker in the tire widthdirection).

Herein, when the tire is provided with a plurality of breakers, thelength of the breaker in the tire width direction refers to the lengthin the tire width direction of the breaker that is the longest in thetire width direction, among the plurality of breakers.

Herein, the tread contact width is determined as follows. First, ano-load and normal condition tire with a normal internal pressuremounted on a normal rim is contacted with a plane at a camber angle of 0degrees while a normal load is applied to the tire, and then the axiallyoutermost contact positions of the tire are each defined as “contactedge Te”. The distance in the tire axis direction between the contactedges Te and Te is defined as a tread contact width TW. The dimensionsand other characteristics of tire components are determined under theabove normal conditions, unless otherwise stated.

The “normal rim” refers to a rim specified for each tire by standards ina standard system including standards according to which tires areprovided, and may be “standard rim” in JATMA, “design rim” in TRA, or“measuring rim” in ETRTO. Moreover, the “normal internal pressure”refers to an air pressure specified for each tire by standards in astandard system including standards according to which tires areprovided, and may be “maximum air pressure” in JATMA, a maximum valueshown in Table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” inTRA, or “inflation pressure” in ETRTO. In the case of tires forpassenger vehicles, the normal internal pressure is 180 kPa.

The “normal load” refers to a load specified for each tire by standardsin a standard system including standards according to which tires areprovided, and may be “maximum load capacity” in JATMA, a maximum valueshown in Table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” inTRA, or “load capacity” in ETRTO. In the case of tires for passengervehicles, the normal load is 88% of the above-specified load.

The rotational speed of the tire during the application of the sealantis not particularly limited. To provide more suitable effects, therotational speed is preferably 5 m/min or higher, more preferably 10m/min or higher, but preferably 30 m/min or lower, more preferably 20m/min or lower. If the rotational speed is lower than 5 m/min or higherthan 30 m/min, a sealant having a uniform thickness cannot be easilyapplied.

When a non-contact displacement sensor is used, the risk of troublescaused by adhesion of the sealant to the sensor can be reduced. Thenon-contact displacement sensor is not particularly limited as long asthe sensor can measure the distance between the inner periphery of thetire and the tip of the nozzle. Examples include laser sensors,photosensors, and capacitance sensors. These sensors may be used aloneor in combinations of two or more. For measurement of rubber, lasersensors or photosensors are preferred among these, with laser sensorsbeing more preferred. When a laser sensor is used, the distance betweenthe inner periphery of the tire and the tip of the nozzle can bedetermined as follows: the inner periphery of the tire is irradiatedwith a laser; the distance between the inner periphery of the tire andthe tip of the laser sensor is determined based on the reflection of thelaser; and the distance between the tip of the laser sensor and the tipof the nozzle is subtracted from the determined distance.

The location of the non-contact displacement sensor is not particularlylimited as long as the distance between the inner periphery of the tireand the tip of the nozzle before the application of the sealant can bemeasured. The sensor is preferably attached to the nozzle, morepreferably in a location to which the sealant will not adhere.

The number, size, and other conditions of the non-contact displacementsensor are also not particularly limited.

Since the non-contact displacement sensor is vulnerable to heat, thesensor is preferably protected with a heat insulator or the like and/orcooled with air or the like to avoid the influence of heat from the hotsealant discharged from the nozzle. This improves the durability of thesensor.

Although the first embodiment has been described based on an example inwhich the tire, not the nozzle, is moved in the width and radialdirections of the tire, the nozzle, not the tire, may be moved, or boththe tire and the nozzle may be moved.

The rotary drive device preferably includes a means to increase thewidth of a tire at a bead portion. In the application of the sealant toa tire, increasing the width of the tire at a bead portion allows thesealant to be easily applied to the tire. Particularly when the nozzleis introduced near the inner periphery of the tire mounted on the rotarydrive device, the nozzle can be introduced only by parallel movement ofthe nozzle, which facilitates the control and improves productivity.

Any means that can increase the width of a tire at a bead portion can beused as the means to increase the width of a tire at a bead portion.Examples include a mechanism in which two devices each having aplurality of (preferably two) rolls which have a fixed positionalrelationship with each other are used and the devices move in the tirewidth direction. The devices maybe inserted from both sides through theopening of the tire into the inside and allowed to increase the width ofthe tire at a bead portion.

In the production method, since the sealant which has been mixed in, forexample, a twin screw kneading extruder and in which the crosslinkingreaction in the extruder is suppressed is directly applied to the tireinner periphery, the crosslinking reaction begins upon the applicationand the sealant adheres well to the tire inner periphery and, at thesame time, the crosslinking reaction more suitably proceeds, whereby aself-sealing tire having high sealing performance can be produced. Thus,the self-sealing tire with the sealant applied thereto does not needfurther crosslinking, thereby offering good productivity.

The self-sealing tire with the sealant applied thereto maybe furthersubjected to a crosslinking step, if necessary.

The self-sealing tire is preferably heated in the crosslinking step.This improves the rate of crosslinking of the sealant and allows thecrosslinking reaction to more suitably proceed so that the self-sealingtire can be produced with higher productivity. The tire may be heated byany method, including known methods, but it may suitably be heated in anoven. The crosslinking step may be carried out, for example, by placingthe self-sealing tire in an oven at 70° C. to 190° C., preferably 150°C. to 190° C., for 2 to 15 minutes.

The tire is preferably rotated in the circumferential direction of thetire during the crosslinking because then flowing of even thejust-applied, easily flowing sealant can be prevented and thecrosslinking reaction can be accomplished without deterioration ofuniformity. The rotational speed is preferably 300 to 1, 000 rpm.Specifically, for example, an oven equipped with a rotational mechanismmay be used.

Even when the crosslinking step is not additionally performed, the tireis preferably rotated in the circumferential direction of the tire untilthe crosslinking reaction of the sealant is completed. In this case,flowing of even the just-applied, easily flowing sealant can beprevented and the crosslinking reaction can be accomplished withoutdeterioration of uniformity. The rotational speed is the same asdescribed for the crosslinking step.

In order to improve the rate of crosslinking of the sealant, the tire ispreferably preliminarily warmed before the application of the sealant.This allows for the production of self-sealing tires with higherproductivity. The temperature for pre-heating the tire is preferably 40°C. to 100° C., more preferably 50° C. to 70° C. When the tire ispre-heated within the temperature range indicated above, thecrosslinking reaction suitably begins upon the application and moresuitably proceeds so that a self-sealing tire having high sealingperformance can be produced. Moreover, when the tire is pre-heatedwithin the temperature range indicated above, the crosslinking step isnot necessary and thus the self-sealing tire can be produced with highproductivity.

In general, continuous kneaders (especially twin screw kneadingextruders) are continuously operated. In the production of self-sealingtires, however, tires need to be replaced one after another uponcompletion of the application of the sealant to one tire. Here, in orderto produce higher quality self-sealing tires while reducingdeterioration of productivity, the following method (1) or (2) maybeused. The method (1) or (2) may be appropriately selected depending onthe situation, in view of the following disadvantages: deterioration inquality in the method (1) and an increase in cost in the method (2).

(1) The feed of the sealant to the inner periphery of the tire iscontrolled by running or stopping the continuous kneader and all thefeeders simultaneously.

Specifically, upon completion of the application to one tire, thecontinuous kneader and all the feeders may be simultaneously stopped,the tire may be replaced with another tire, preferably within oneminute, and the continuous kneader and all the feeders may besimultaneously allowed to run to restart the application to the tire. Byreplacing tires quickly, preferably within one minute, the deteriorationin quality can be reduced.

(2) The feed of the sealant to the inner periphery of the tire iscontrolled by switching flow channels while allowing the continuouskneader and all the feeders to keep running.

Specifically, the continuous kneader may be provided with another flowchannel in addition to a nozzle for direct feeding to the tire innerperiphery, and the prepared sealant may be discharged from the anotherflow channel after completion of the application to one tire untilcompletion of the replacement of tires. According to this method, sinceself-sealing tires can be produced while the continuous kneader and allthe feeders are kept running, the produced self-sealing tires can havehigher quality.

Non-limiting examples of carcass cords that can be used in the carcassof the self-sealing tire described above include fiber cords and steelcords. Steel cords are preferred among these. In particular, steel cordsformed of hard steel wire materials specified in JIS G 3506 aredesirable. The use of strong steel cords, instead of commonly used fibercords, as carcass cords in the self-sealing tire can greatly improveside cut resistance (resistance to cuts formed in the tire side portionsdue to driving over curbs or other reasons) and thereby further improvethe puncture resistance of the entire tire including the side portions.

The steel cord may have any structure. Examples include steel cordshaving a 1×n single strand structure, steel cords having a k+m layerstrand structure, steel cords having a 1×n bundle structure, and steelcords having an m×n multi-strand structure. The term “steel cord havinga 1×n single strand structure” refers to a single-layered twisted steelcord prepared by intertwining n filaments. The term “steel cord having ak+m layer strand structure” refers to a steel cord having a two-layeredstructure in which the two layers are different from each other in twistdirection and twist pitch, and the inner layer includes k filamentswhile the outer layer includes m filaments. The term “steel cord havinga 1×n bundle structure” refers to a bundle steel cord prepared byintertwining bundles of n filaments. The term “steel cord having an m×nmulti-strand structure” refers to a multi-strand steel cord prepared byintertwining m strands prepared by first twisting n filaments together.Here, n represents an integer of 1 to 27; k represents an integer of 1to 10; and m represents an integer of 1 to 3.

The twist pitch of the steel cord is preferably 13 mm or less, morepreferably 11 min or less, but preferably 5 mm or more, more preferably7 mm or more.

The steel cord preferably contains at least one piece of preformedfilament formed in the shape of a spiral. Such a preformed filamentprovides a relatively large gap within the steel cord to improve rubberpermeability and also maintain the elongation under low load, so that amolding failure during vulcanization can be prevented.

The surface of the steel cord is preferably plated with brass, Zn, orother materials to improve initial adhesion to the rubber composition.

The steel cord preferably has an elongation of 0.5% to 1.5% under a loadof 50 N. If the elongation under a load of 50 N is more than 1.5%, thereinforcing cords may show reduced elongation under high load and thusdisturbance absorption may not be maintained. Conversely, if theelongation under a load of 50 N is less than 0.5%, the cords may notshow sufficient elongation during vulcanization and thus a moldingfailure may occur. In view of the above, the elongation under a load of50 N is more preferably 0.7% or more, but more preferably 1.3% or less.

The endcount of the steel cords is preferably 20 to 50 (ends/5 cm).

Second Embodiment

The studies of the present inventors have further revealed that the useof the method according to the first embodiment alone has the followingdisadvantage: a sealant having a generally string shape is occasionallydifficult to attach to the inner periphery of a tire and can easily peeloff especially at the attachment start portion. A second embodiment ischaracterized in that in the method for producing a self-sealing tire,the sealant is attached under conditions where the distance between theinner periphery of the tire and the tip of the nozzle is adjusted to adistance d₁ and then to a distance d₂ larger than the distance d₁. Inthis case, the distance between the inner periphery of the tire and thetip of the nozzle is shortened at the beginning of the attachment, sothat the width of the sealant corresponding to the attachment startportion can be increased. As a result, a self-sealing tire can be easilyproduced in which a generally string-shaped adhesive sealant iscontinuously and spirally attached at least to the inner periphery ofthe tire that corresponds to a tread portion, and at least one of thelongitudinal ends of the sealant forms a wider portion having a widthlarger than that of the longitudinally adjoining portion. In thisself-sealing tire, a portion of the sealant that corresponds to startingof attachment has a larger width to improve adhesion of this portion sothat peeling of this portion of the sealant can be prevented.

The description of the second embodiment basically includes onlyfeatures different from the first embodiment, and the contentsoverlapping the description of the first embodiment are omitted.

FIG. 5 are enlarged views showing the vicinity of the tip of the nozzleincluded in the applicator shown in FIG. 1. FIG. 5(a) illustrates astatus immediately after attachment of the sealant is started and FIG.5(b) illustrates a status after a lapse of a predetermined time.

FIGS. 5 each show a cross section of a part of a tire 10 taken along aplane including the circumferential and radial directions of the tire.In FIGS. 5, the width direction (axis direction) of the tire isindicated by an arrow X, the circumferential direction of the tire isindicated by an arrow Y, and the radial direction of the tire isindicated by an arrow Z.

According to the second embodiment, the tire 10 formed through avulcanization step is first mounted on a rotary drive device, and anozzle 30 is inserted into the inside of the tire 10. Then, as shown inFIGS. 1 and 5, the tire 10 is rotated and simultaneously moved in thewidth direction while a sealant 20 is discharged from the nozzle 30,whereby the sealant is continuously applied to the inner periphery 11 ofthe tire 10. The tire 10 is moved in the width direction according to,for example, the pre-entered profile of the inner periphery 11 of thetire 10.

Since the sealant 20 is adhesive and has a generally string shape, thesealant 20 is continuously and spirally attached to the inner periphery11 of the tire 10 that corresponds to a tread portion.

In this process, as shown in FIG. 5(a), the sealant 20 is attached underconditions where the distance between the inner periphery 11 of the tire10 and the tip 31 of the nozzle 30 is adjusted to a distance d₁ for apredetermined time from the start of the attachment. Then, after a lapseof the predetermined time, as shown in FIG. 5(b), the tire 10 is movedin the radial direction to change the distance to a distance d₂ largerthan the distance d₁ and the sealant 20 is attached.

The distance may be changed from the distance d₂ back to the distance d₁before completion of the attachment of the sealant. In view ofproduction efficiency and tire weight balance, the distance d₂ ispreferably maintained until the sealant attachment is completed.

Preferably, the distance d₁ is kept constant for a predetermined timefrom the start of the attachment, and after a lapse of the predeterminedtime the distance d₂ is kept constant, although the distances d₁ and d₂are not necessarily constant as long as they satisfy the relation of d₁<d₂.

The distance d₁ is not particularly limited. To provide more suitableeffects, the distance d₁ is preferably 0.3 mm or more, more preferably0.5 mm or more. If the distance d₁ is less than 0.3 mm, the tip of thenozzle is too close to the inner periphery of the tire, so that thesealant can easily adhere to the nozzle and the nozzle may need to becleaned more frequently. The distance d₁ is also preferably 2 mm orless, more preferably 1 mm or less. If the distance d₁ is more than 2mm, the effect produced by the formation of a wider portion may not besufficient.

The distance d₂ is also not particularly limited. To provide moresuitable effects, the distance d₂ is preferably 0.3 mm or more, morepreferably 1 mm or more, but preferably 3 mm or less, more preferably 2mm or less. The distance d₂ is preferably the same as the controlleddistance d₀ described above.

Herein, the distances d₁ and d₂ between the inner periphery of the tireand the tip of the nozzle each refer to the distance in the radialdirection of the tire between the inner periphery of the tire and thetip of the nozzle.

The rotational speed of the tire during the attachment of the sealant isnot particularly limited. To provide more suitable effects, therotational speed is preferably 5 m/min or higher, more preferably 10m/min or higher, but preferably 30 m/min or lower, more preferably 20m/min or lower. If the rotational speed is lower than 5 m/min or higherthan 30 m/min, a sealant having a uniform thickness cannot be easilyattached.

The self-sealing tire according to the second embodiment can be producedthrough the steps described above.

FIG. 6 is an explanatory view schematically showing an example of asealant attached to a self-sealing tire according to the secondembodiment.

The generally string-shaped sealant 20 is wound in the circumferentialdirection of the tire and continuously and spirally attached. Here, oneof the longitudinal ends of the sealant 20 forms a wider portion 21having a width larger than that of the longitudinally adjoining portion.The wider portion 21 corresponds to the attachment start portion of thesealant.

The width of the wider portion of the sealant (width of the widerportion of the applied sealant, length indicated by W₁ in FIG. 6) is notparticularly limited. To provide more suitable effects, the width of thewider portion is preferably 103% or more, more preferably 110% or more,still more preferably 120% or more of the width of the sealant otherthan the wider portion (length indicated by W₀ in FIG. 6). If it is lessthan 103%, the effect produced by the formation of a wider portion maynot be sufficient. The width of the wider portion of the sealant is alsopreferably 210% or less, more preferably 180% or less, still morepreferably 160% or less of the width of the sealant other than the widerportion. If it is more than 210%, the tip of the nozzle needs to beplaced excessively close to the inner periphery of the tire to form awider portion, with the result that the sealant can easily adhere to thenozzle and the nozzle may need to be cleaned more frequently. Inaddition, tire weight balance may be impaired.

The width of the wider portion of the sealant is preferablysubstantially constant in the longitudinal direction but may partiallybe substantially not constant. For example, the wider portion may have ashape in which the width is the largest at the attachment start portionand gradually decreases in the longitudinal direction. The substantiallyconstant width as used herein means that the width varies within a rangeof 90% to 110%, preferably 97% to 103%, more preferably 98% to 102%,still more preferably 99% to 101%.

The length of the wider portion of the sealant (length of the widerportion of the applied sealant, length indicated by L₁ in FIG. 6) is notparticularly limited. To provide more suitable effects, the length ispreferably less than 650 mm, more preferably less than 500 mm, stillmore preferably less than 350 mm, particularly preferably less than 200mm. If the length is 650 mm or more, the tip of the nozzle is placedclose to the inner periphery of the tire for a longer period of time, sothat the sealant can easily adhere to the nozzle and the nozzle may needto be cleaned more frequently. In addition, tire weight balance may beimpaired. The sealant preferably has a shorter wider portion. However,for control of the distance between the inner periphery of the tire andthe tip of the nozzle, the limit of the length of the wider portion isabout 10 mm.

The width of the sealant other than the wider portion (width of theapplied sealant other than the wider portion, length indicated by W₀ inFIG. 6) is not particularly limited. To provide more suitable effects,the width is preferably 0.8 mm or more, more preferably 1. 3 mm or more,still more preferably 1.5 mm or more. If the width is less than 0.8 mm,the number of turns of the sealant around the inner periphery of thetire may increase, reducing production efficiency. The width of thesealant other than the wider portion is also preferably 18 mm or less,more preferably 13 mm or less, still more preferably 9.0 mm or less,particularly preferably 7.0 mm or less, most preferably 6.0 mm or less,still most preferably 5.0 mm or less. If the width is more than 18 mm, aweight imbalance may be more likely to occur. W₀ is preferably the sameas the above-described W.

The width of the sealant other than the wider portion is preferablysubstantially constant in the longitudinal direction but may partiallybe substantially not constant.

The width of the area where the sealant is attached (hereinafter alsoreferred to as the width of the attachment area or the width of thesealant layer, and corresponding to a length equal to W₁+6×W₀ in FIG. 6)is not particularly limited. To provide more suitable effects, the widthis preferably 80% or more, more preferably 90% or more, still morepreferably 100% or more, but preferably 120% or less, more preferably110% or less, of the tread contact width.

To provide more suitable effects, the width of the sealant layer ispreferably 85% to 115%, more preferably 95% to 105% of the width of thebreaker of the tire (the length of the breaker in the tire widthdirection).

In the self-sealing tire according to the second embodiment, the sealantis preferably attached without overlapping in the width direction andmore preferably without gaps.

In the self-sealing tire according to the second embodiment, the otherlongitudinal end (the end corresponding to the attachment endingportion) of the sealant may also form a wider portion having a widthlarger than that of the longitudinally adjoining portion.

The thickness of the sealant (thickness of the applied sealant or thesealant layer, length indicated by D in FIG. 8) is not particularlylimited. To provide more suitable effects, the thickness of the sealantis preferably 1.0 mm or more, more preferably 1.5 mm or more, still morepreferably 2.0 minor more, particularly preferably 2.5 mm or more, butpreferably 10 mm or less, more preferably 8.0 mm or less, still morepreferably 5.0 mm or less. If the thickness is less than 1.0 mm, then apuncture hole formed in the tire is difficult to reliably seal. Also, athickness of more than 10 mm is not preferred because tire weightincreases, although with little improvement in the effect of sealingpuncture holes.

The sealant preferably has a substantially constant thickness (thicknessof the applied sealant or the sealant layer). In this case, thedeterioration of tire uniformity can be further prevented and aself-sealing tire having much better weight balance can be produced.

The ratio of the thickness of the sealant (thickness of the appliedsealant or the sealant layer, length indicated by D in FIG. 8) to thewidth of the sealant other than the wider portion (width of the appliedsealant other than the wider portion, length indicated by W₀ in FIG. 6)[(thickness of sealant)/(width of sealant other than wider portion)] ispreferably 0.6 to 1.4, more preferably 0.7 to 1.3, still more preferably0.8 to 1.2, particularly preferably 0.9 to 1.1. A ratio closer to 1.0results in a sealant having an ideal string shape, so that aself-sealing tire having high sealing performance can be produced withhigher productivity.

To provide more suitable effects, the cross-sectional area of thesealant (cross-sectional area of the applied sealant, area calculated byD×W in FIG. 8) is preferably 0.8 mm² or more, more preferably 1.95 mm²or more, still more preferably 3.0 mm² or more, particularly preferably3.75 mm² or more, but preferably 180 mm² or less, more preferably 104mm² or less, still more preferably 45 mm² or less, particularlypreferably 35 mm² or less, most preferably 25 mm² or less.

According to the second embodiment, even when the sealant has aviscosity within the range indicated earlier, and particularly arelatively high viscosity, widening a portion of the sealant thatcorresponds to starting of attachment can improve adhesion of thisportion so that peeling of this portion of the sealant can be prevented.

The self-sealing tire according to the second embodiment is preferablyproduced as described above. However, the self-sealing tire may beproduced by any other appropriate method as long as at least one of theends of the sealant is allowed to form a wider portion.

Although the above descriptions, and particularly the description of thefirst embodiment, explain the case where a non-contact displacementsensor is used in applying the sealant to the inner periphery of thetire, the sealant may be applied to the inner periphery of the tirewhile controlling the movement of the nozzle and/or the tire accordingto the pre-entered coordinate data, without measurement using anon-contact displacement sensor.

Self-sealing tires including a sealant layer located radially inside aninnerliner can be produced as described above or by other methods. Inparticular, the sealant layer is preferably formed by applying a sealantto the inner periphery of a vulcanized tire because of advantages suchas that problems caused by flowing of the sealant or other reasons areless likely to occur and that this method can be responsive to changesin tire size by programming. For easy handling of the sealant and highproductivity, the sealant layer is also preferably formed bysequentially preparing a sealant by mixing raw materials including acrosslinking agent using a continuous kneader, and sequentially applyingthe sealant to the inner periphery of a tire.

According to the present invention, after the production of aself-sealing tire including a sealant layer located radially inside aninnerliner as described above or by other methods, in other words, aftera sealant layer is formed radially inside an innerliner of a tire by thestep of continuously and spirally applying a generally string-shapedsealant to the inner periphery of a vulcanized tire, the further step isperformed of attaching a resonator including a tube with an opening, anda cavity connected to the tube after the application of the sealant.

<Step of Attaching a Resonator>

In the step of attaching a resonator, a resonator is attached andlocated radially inside the sealant layer formed radially inside theinnerliner of the tire.

(First Pneumatic Tire)

In the case of the first pneumatic tire including a resonator whoseopening is provided to face the inside of the tire, a resonator can beattached and located radially inside the sealant layer in the tire whileallowing the opening of the resonator to face the inside of the tire.

As the sealant forming the sealant layer in the first pneumatic tire isadhesive, by bringing a resonator into contact with the sealant layer,the resonator can be easily provided radially inside the sealant layerin the tire while adhering well to it. Moreover, in spite of utilizingthe adhesiveness, the deterioration of sealing performance can beprevented so that the tire can maintain the sealing performance.

The step of attaching a resonator for the first pneumatic tire may becarried out by bringing an appropriately selected sound-absorbingresonator into contact with the adhesive sealant layer. The resonator isattached to the inner periphery of the tire. Particularly in view ofsound-absorbing properties, practical utility, and other properties, theresonator is preferably attached to the tire inner peripherycorresponding to a tread portion.

The resonator used in the first pneumatic tire may be a Helmholtz-typeresonator including a tube with an opening, and a cavity (sub airchamber) connected to the tube. When the opening of the resonator isprovided to face the inside of the tire, the vibrational energy of soundwaves is converted to thermal energy due to the flow friction in thetube and the reflection of intake sound in the cavity, whereby thecavity resonance (road noise) in the tire can be absorbed.

The sound-absorbing resonator may be, for example, an embodiment asshown in the schematic view of FIG. 10. The resonator 300 in FIG. 10includes a tube 301 with a length L having an opening 301 a with anopening area S, and also includes a rectangular parallelepiped cavity302 with an inner width A₁, an inner length B₁, and an inner height C₁(volume of cavity V=A₁×B₁×C₁) which communicates with and is connectedto the tube 301.

The sound-absorbing effect for tire cavity resonance is specificallydescribed. Tire cavity resonance can be reduced by controlling (tuning)the tube 301 so that the resonator 300 has a resonant frequency that isequal or substantially equal to the frequency of the tire cavityresonance.

The resonant frequency f₀ of the cavity can be determined by theequation below. If necessary, an open end correction may be applied tothe length L (m) of the tube and other parameters.

$f_{0} = {\frac{C}{2\pi}\sqrt{\frac{S}{LV}}}$

-   Cross-sectional area of tube (area of opening): S (m²)-   Length of tube: L (m)-   Volume (capacity) of cavity: V (m³)-   Sound velocity: C (m/s)

Then, tire cavity resonance can be reduced by controlling (tuning) thecross-sectional area (the area of the opening of the tube 110) and thelength of the tube so that the resonator 100 has a resonant frequencythat is equal or substantially equal to the tire cavity resonanceaccording to the above equation.

In the case of the first pneumatic tire, tire cavity resonance can bereduced by using a resonator tuned (controlled) to 130 to 330 Hz,preferably 180 to 280 Hz.

The size, number, and wall thickness of the resonator in the firstpneumatic tire may be appropriately selected depending on the size ofthe tire, sound-absorbing effect, and other factors. With regard to thenumber of resonators, for example, since the use of a large resonatorcan cause imbalance, it is desirable to use a plurality of smallresonators. The use of a larger number (total number) of resonatorstends to lead to a greater reduction in tire cavity resonance, and thenumber is preferably 4 or more, more preferably 12 or more, still morepreferably 24 or more.

In the first pneumatic tire, the resonator is preferably deformed and/orbroken upon puncture with a nail or other foreign bodies. If a resonatorformed of a high strength material is used to prevent the damage by anail, upon puncture with a nail, the sealant adheres to the resonatorand peels off, thereby resulting in deterioration of air-sealingproperties. In contrast, if a resonator is deformed and/or broken uponpuncture, the sealant layer will not be affected by the deformationand/or breakage so that the deterioration of air-sealing properties canbe reduced. Although the sound-absorbing effect is lost by thedeformation and/or breakage of the resonator, the desired noisereduction effect can also be achieved by provision of a plurality ofresonators. The expression “the resonator is deformed and/or broken”herein means that a change occurs in the original adhesion (attachment)of the resonator, such as: the resonator is broken by a nail or thelike; the resonator is separated from the adhesive (attachment) surfaceof the sealant layer; or the position of the resonator provided ismoved. A deformable resonator may be produced from, for example, alightweight material with excellent strength and heat resistance such aspolypropylene, cardboard, corrugated cardboard, or nonwoven fabric.

The resonator in the first pneumatic tire may suitably be, for example,one in which the cavity of the resonator has no bottom surface, but thesurface of a sealant layer is provided as a substitute for the bottomsurface. For example, in the case where the resonator 300 in FIG. 10 hasno bottom surface, specifically, where the resonator has no bottomsurface defined by the width A₁ and length B₁, the side with no bottomsurface is adhered (attached) to a sealant layer. This prevents thesealant layer from peeling off when the resonator is separated off uponpuncture with a nail, thereby leading to good air-sealing properties.Furthermore, such a resonator can be easily produced. The bottom surfaceof the cavity herein refers to the surface of the cavity on the sidefacing the tube and is, in FIG. 10, defined by the width A₁ and lengthB₁.

In the first pneumatic tire, preferably resonators are circumferentiallyprovided at substantially equally spaced intervals. Also preferably,resonators tuned (controlled) to the same frequency are providedcircumferentially symmetrically about the axis of the tire. In view ofuniformity and prevention of imbalance, it is desirable to placeresonators at substantially equally spaced intervals or to symmetricallyplace resonators of the same type. As a result, not only can the effectof reducing resonance be achieved, but also vibration can besufficiently suppressed.

FIG. 11 is a schematic view (circumferential cross-sectional view of thetire) of a self-sealing tire as a suitable example of the firstpneumatic tire including a resonator whose opening is provided to facethe inside of the tire. In the self-sealing tire, resonators arecircumferentially provided at substantially equally spaced intervals,and the resonators tuned to the same frequency are providedcircumferentially symmetrically about the axis of the tire.

The self-sealing tire 310 shown in FIG. 11 includes a sealant layer 312formed radially inside an innerliner in a tire component 311 (includingthe innerliner). Resonators 313 a and 313 b tuned to the same frequency(for example 220 Hz) and resonators 314 a and 314 b tuned to the samefrequency (for example 220 Hz) are also provided on the inner peripheryof the sealant layer 312. The opening of each resonator is provided toface the inside of the tire. Moreover, the resonators are providedsymmetrically about the axis (not shown, the center part of the figure)of the tire, and the resonators are provided at substantially equallyspaced intervals (1/4 in the tire circumferential direction). With sucha structure, not only can the effect of reducing tire cavity resonancebe sufficiently achieved, but also vibration can be prevented. AlthoughFIG. 11 shows an exemplary embodiment in which the sealant layer 312 isformed, the same effect can be obtained in a first pneumatic tire inwhich an adhesive layer that can adhere to the resonators 314 a and 314b is formed in place of the sealant layer 312.

FIG. 12 is an exemplary photograph of a resonator attached to the innerperiphery of a sealant layer as an example of the first pneumatic tireincluding a resonator whose opening is provided to face the inside ofthe tire.

(Second Pneumatic Tire)

In the case of the second pneumatic tire including a resonator whoseopening is provided to penetrate outside of the tire, a resonator can beattached and located radially inside the sealant layer in the tire whileallowing the opening of the resonator to penetrate from the radiallyinner side of the sealant layer to the outside of the tire.

As the sealant forming the sealant layer in the second pneumatic tire isadhesive, by bringing a resonator into contact with the sealant layer,the resonator can be easily provided radially inside the sealant layerin the tire while adhering well to it. Moreover, leakage of the air inthe tire through the opening can be prevented due to the closeattachment achieved by virtue of the adhesiveness, whereby the retentionof the air in the tire can be maintained. It is also possible to retainthe air even upon puncture because the nail does not interfere with theresonator and the sealant exhibits sealing performance.

The step of attaching a resonator for the second pneumatic tire can becarried out as in the case of the first pneumatic tire by bringing anappropriately selected sound-absorbing. resonator into contact with anadhesive sealant layer. The resonator is attached to the inner peripheryof the tire. Particularly in view of sound-absorbing properties,practical utility, and other properties, the resonator is preferablyattached to the tire inner periphery corresponding to a tread portion.

The resonator in the second pneumatic tire may be a Helmholtz-typeresonator including a tube with an opening, and a cavity (sub airchamber) connected to the tube as in the case of the first pneumatictire. When the opening of the resonator is provided to penetrate outsideof the tire, the vibrational energy of sound waves is converted tothermal energy due to the flow friction in the tube and the reflectionof intake sound in the cavity, whereby the air column resonance (patternnoise) in the tire grooves can be absorbed.

Examples of the sound-absorbing resonator include those mentioned forthe first pneumatic tire. The air column resonance in the tire groovescan be reduced by the control (tuning) as described above.

In the case of the second pneumatic tire, the air column resonance inthe tire grooves can be reduced by using a resonator tuned (controlled)to 500 Hz to 2 kHz.

The size, number, and wall thickness of the resonator in the secondpneumatic tire may be appropriately selected depending on the size ofthe tire, sound-absorbing effect, and other factors. With regard to thenumber of resonators, for example, since the use of a large resonatorcan cause imbalance, it is desirable to use a plurality of smallresonators. The use of a larger number (total number) of resonatorstends to lead to a greater reduction in the air column resonance in thetire grooves, and the number is preferably 50 or more, more preferably300 or more, still more preferably 400 or more.

In the second pneumatic tire, the resonator may be deformed and/orbroken upon puncture with a nail or other foreign bodies as in the firstpneumatic tire.

Examples of the resonator in the first pneumatic tire include, inaddition to the conventional resonators as shown in, for example, FIG.10, resonators in which a tube is provided separately from a cavityhaving no upper surface. For example, in the case where the resonator300 in FIG. 10 has no upper surface (surface bonding to the tube),specifically, where the resonator has no upper surface defined by thewidth A₁ and length B₁ which bonds to the tube, the tube is placed topenetrate outside of the tire while the side with no upper surface isadhered (attached) to a sealant layer. This ensures air-sealingproperties and air retention properties. Furthermore, such a resonatorcan be easily produced.

Like the first pneumatic tire, the second pneumatic tire may anembodiment in which resonators are circumferentially provided atsubstantially equally spaced intervals or an embodiment in whichresonators tuned (controlled) to the same frequency are providedcircumferentially symmetrically about the axis of the tire.

As described above, FIG. 11 shows an example of the first pneumatic tireincluding a resonator whose opening is provided to face the inside ofthe tire. The second pneumatic tire may be the same embodiment, exceptthat the opening of the resonator is provided to penetrate outside ofthe tire (not shown).

FIG. 13 is a cross-sectional view in the meridional direction of a partof a tire including a resonator whose opening is provided to penetrate acircumferential longitudinal groove of the tire as an example of thesecond pneumatic tire including a resonator whose opening is provided topenetrate outside of the tire. FIG. 14 is a schematic view of a tireshowing circumferential longitudinal grooves and lateral grooves of thetire.

In the self-sealing tire 320 shown in FIG. 13, circumferentiallongitudinal grooves 322 are formed on the surface of a tread 321 in atread portion. A tuned resonator 324 is also provided on the innerperiphery of a sealant layer 323. The opening of the resonator 324 isprovided to penetrate the surface of the circumferential longitudinalgroove 322 of the tire. With such a structure, the effect of reducingthe air column resonance in the tire longitudinal grooves can besignificantly achieved. Although the penetration may cause air leakage,the resonator can be closely attached by taking advantage of theadhesiveness of the sealant, and leakage of the air in the tire throughthe opening can be prevented due to the close attachment achieved byvirtue of the adhesiveness, whereby the retention of the air in the tirecan be maintained. It is also possible to retain the air even uponpuncture because the sealant exhibits sealing performance. Practicalutility can also be ensured.

Although FIG. 13 shows an example in which the resonator is provided atthe longitudinal groove 322, a resonator may be provided at a lateralgroove 325 in FIG. 14. In this case, the resonance in the lateralgrooves can be reduced.

EXAMPLES

The present invention is specifically described with reference to, butnot limited to, examples below.

The chemicals used in the examples are listed below.

Butyl rubber A: Regular butyl 065 (available from Japan Butyl Co., Ltd.,Mooney viscosity ML₁₊₈ at 125° C.: 32)

Liquid polymer A: Nisseki polybutene HV300 (available from JX Nippon Oil& Energy Corporation, kinematic viscosity at 40° C.: 26,000 mm²/s,kinematic viscosity at 100° C.: 590 mm²/s, number average molecularweight: 1,400)

Liquid polymer B: Nisseki polybutene HV1900 (available from JX NipponOil & Energy Corporation, kinematic viscosity at 40° C.: 160,000 mm²/s,kinematic viscosity at 100° C.: 3,710 mm²/s, number average molecularweight: 2,900)

Plasticizer: DOP (dioctyl phthalate, available from Showa Chemical,specific gravity: 0.96, viscosity: 81 mPs·s)

Carbon black: N330 (available from Cabot Japan K.K., HAF grade, DBP oilabsorption: 102 ml/100 g)

Crosslinking activator: VULNOC GM (available from Ouchi Shinko ChemicalIndustrial Co., Ltd., p-benzoquinone dioxime)

Crosslinking agent: NYPER NS (available from NOF Corporation, dibenzoylperoxide (40% dilution, dibenzoyl peroxide: 40%, dibutyl phthalate:48%), the amount shown in Table 1 is the net benzoyl peroxide content)

According to the formulation shown in Table 1, the chemicals wereintroduced into a twin screw kneading extruder as follows: the butylrubber A, carbon black, and crosslinking activator were introduced fromthe upstream supply port; the liquid polymer B was introduced from themidstream supply port; and the liquid polymer A, plasticizer, andcrosslinking agent were introduced from the downstream supply port. Theywere kneaded at 200 rpm at a barrel temperature of 100° C. to prepare asealant. The liquid polymers were heated to 50° C. before theintroduction from the supply ports.

(Time for Kneading Materials)

Time for mixing butyl rubber A, carbon black, and crosslinkingactivator: 2 minutes

Time for mixing liquid polymer B: 2 minutes

Time for mixing liquid polymer A, plasticizer, and crosslinking agent:1.5 minutes

TABLE 1 Sealant Formulation amount Butyl rubber A 100 (parts by mass)(ML₁₊₈ at 125° C.: 32) Liquid polymer A 100 (Kinematic viscosity at 100°C.: 590) Liquid polymer B 100 (Kinematic viscosity at 100° C.: 3710)Plasticizer (DOP) 10 Carbon black (N330) 10 Crosslinking activator 10(p-benzoquinone dioxime) Crosslinking agent 10 (Dibenzoyl peroxide)

[Second Pneumatic Tire] Examples 1 to 3 <Production of Self-SealingTire>

The sealant (at 100° C.) sequentially prepared as above was extrudedfrom the twin screw kneading extruder through the nozzle andcontinuously and spirally attached (spirally applied) as shown in FIGS.1 to 4 to the inner periphery of a tire (215/55R17, 94W, rim: 17×8J,cross-sectional area of cavity of tire mounted on rim: 194 cm²,vulcanized, rotational speed of tire: 12 m/min, pre-heating temperature:40° C., width of tire breaker: 180 mm) mounted on a rotary drive deviceto allow the sealant (viscosity at 40° C.: 10,000 Pa·s, generally stringshape, thickness: 3 mm, width: 4 mm) to form a sealant layer with athickness of 3 mm and a width of the attachment area of 180 mm. Further,resonators each having the shape (with an upper surface) and the tunedfrequency indicated in Table 2 were placed radially inside the sealantlayer formed in the tire by taking advantage of the adhesiveness of thesealant, while allowing the opening (end) of each resonator to penetratethe tire groove (see FIG. 13), under the conditions shown in Table 3,including the number of longitudinal tread grooves in the tire, location(longitudinal or lateral tread grooves), number (the number ofresonators in each groove), total number (the total number ofresonators), details of number (the number for each tuned frequency),arrangement in the tread circumferential direction (arranged at equallyspaced intervals or without gaps; symmetry or asymmetry about the tireaxis; putting together the same type), and material (polypropylene,iron). Accordingly, second self-sealing tires were prepared.

The width of the sealant was controlled to be substantially constant inthe longitudinal direction. The viscosity of the sealant was measured at40° C. in conformity with JIS K 6833 using a rotational viscometer.

Examples 4 to 12

<Production of Tire (with No Sealant Layer)>

Tires (second pneumatic tires with no sealant layer) were prepared as inExample 1, except that no sealant layer was formed, and the resonatorswere manually placed on the inner surface of the innerliner under theconditions indicated in Table 3.

Comparative Example 1

A regular tire (pneumatic tire) including no sealant layer and noresonator was used.

The self-sealing tires and tires prepared as above underwent thefollowing evaluations.

<Pattern Noise-Reducing Properties (subjective Noise Test)>

The self-sealing tires or tires (215/55R17, 94W, rim: 17×8J, tire innerperipheral length: 1, 999 mm, initial internal pressure: 230 kPa,ambient temperature: 25° C.) were mounted on all the wheels of afront-engine, front-wheel-drive vehicle of 2,000 cc displacement made inJapan. The “SHAH” noise during driving of the vehicle at 100 km/h wassubjectively evaluated by a driver and expressed as an index, withComparative Example 1 (regular tire) set equal to 100.

A higher index indicates better pattern noise-reducing properties.

<Generation of Vibration (Vibration Test)>

In the subjective noise test, the driver subjectively evaluatedvibration during driving at 120 km/h.

<Air Retention Test>

The self-sealing tire or tire mounted on a rim was allowed to stand at25° C. for seven days. Then, the internal pressure of the tire wasmeasured and expressed as an index, with Comparative Example 1 (regulartire) set equal to 100. A higher index indicates better air retentionproperties.

<Puncture-Repairing Properties (Sealing Performance)>

Ten nails (round nails according to JIS N100, shank diameter: 4.2 mm)were completely driven into a longitudinal groove of the self-sealingtire and then immediately removed. After the tire was allowed to standfor a whole day, the internal pressure of the tire was measured. Theresidual internal pressure (index of air leakage) is expressed as anindex, with Example 2 set equal to 100. A higher index indicates betterpuncture-repairing properties (sealing performance).

TABLE 2 Resonator Frequency (Hz) 400 500 1000 1999 3998 Size (inner A₁(width) 12 10 6 4 2.5 diameter)/cm B₁ (length) 12 10 6 4 2.5 C₁ (height)9.9 9.1 6.3 3.6 2.3 D (Diameter of 1 1 1 1 1 opening area S) L (Tubelength) 9 9 9 9 9

TABLE 3 Second tire Comparative Example Example Example Example ExampleExample Example 1 1 2 3 4 5 6 Resonator Location Absent Longitu-Longitu- Longitu- Lateral Longitu- Longitu- dinal dinal dinal groovedinal dinal groove groove groove groove groove — abcd abcd abcd — b abcdNumber of 0  4  4  4 —  1  4 longitudinal grooves Number 0 120 120 (120)— 50 120 Total number 0 480 480 475 100 50 480 Details 400 Hz — — — — —— — of 500 Hz — 160 160 158 — — — number  1 kHz — 160 160 159 100 50 480 2 kHz — 160 160 158 — — —  4 kHz — — — — — — — Arrangement in — EqualEqual Equal Equal Equal Equal tread circumferential intervals intervalsintervals intervals intervals intervals direction — Symmetry SymmetrySymmetry Symmetry Symmetry Symmetry Material — Iron PP PP Iron Iron IronSealant (with/without) without with with with without without withoutSubjective noise 100  120 120 120 102 104  115 (“SHAH” noise) Generationof vibration No Yes Yes Yes No No No Air retention properties 100  100100 100  99 99  98 Puncture-repairing properties —  90 100 100 — — —Example Example Example Example Example Example 7 8 9 10 11 12 ResonatorLocation Longitu- Longitu- Longitu- Longitu- Longitu- Longitu- dinaldinal dinal dinal dinal dinal groove groove groove groove groove grooveabcd abcd abcd abcd abcd abcd Number of  4  4  4  4  4  4 longitudinalgrooves Number 120 120 120 120 120 120 Total number 480 480 480 480 480480 Details 400 Hz — — 120 — — — of 500 Hz 240 160 120 120 160 160number  1 kHz 240 160 120 120 160 160  2 kHz — 160 120 120 160 160  4kHz — — — 120 — — Arrangement in Equal Equal Equal Equal Arranged Equaltread circumferential intervals intervals intervals intervals withoutgaps intervals direction Symmetry Symmetry Symmetry Symmetry AsymmetryPutting together the same type Material Iron Iron Iron Iron Iron IronSealant (with/without) without without without without without withoutSubjective noise 116 120 113 112 120 120 (“SHAH” noise) Generation ofvibration No No No No Yes Yes Air retention properties  98  98  98  98 98  98 Puncture-repairing properties — — — — — — One longitudinalgroove (b): Resonators were provided at one longitudinal groove b. Fourlongitudinal grooves (a, b, c, d): Resonators were provided evenly atfour longitudinal grooves a, b, c, and d Lateral groove: Resonators wereprovided at lateral grooves. Examples 2 and 3 were evaluated afterremoving nails (Five resonators were broken.)

The self-sealing tires of Examples 1 to 3 (second pneumatic tires)including resonators exhibited sufficiently reduced pattern noise andexcellent air retention properties. In these examples, slight vibrationswere felt, but the vibration levels were practically acceptable. Thepuncture-repairing properties of the tire of Example 1 using an ironmaterial were slightly low, but were practically acceptable.

The tires (with no sealant layer) of Examples 4 to 12 exhibitedsufficiently reduced pattern noise and excellent air retentionproperties. In some of these examples, slight vibrations were felt, butthe vibration levels were practically acceptable.

[First pneumatic tire]

Examples 21 to 23 <Production of Self-Sealing Tire>

First self-sealing tires were prepared as in Example 1, except thatresonators each having the shape (with a bottom surface) and the tunedfrequency indicated in Table 4, instead of Tables 2 and 3, were placedby taking advantage of the adhesiveness of the sealant, while allowingthe opening of each resonator to face the inside of the tire (see FIG.11), under the conditions shown in Table 5, including location (innerequatorial plane), number (the total number of resonators), arrangementin the tread circumferential direction (at equally spaced intervals,symmetry about the tire axis), and material (polypropylene, iron).

The self-sealing tires prepared as above underwent the followingevaluations.

<Cavity Resonance-Reducing Properties (Subjective Noise test)>

The self-sealing tires (215/55R17, 94W, rim: 17×8J, tire innerperipheral length: 1,999 mm, initial internal pressure: 230 kPa, ambienttemperature: 25° C.) were mounted on all the wheels of a front-engine,front-wheel-drive vehicle of 2,000 cc displacement made in Japan. Thetire cavity resonance (road noise) during driving of the vehicle at 100km/h was subjective evaluated by a driver and expressed as an index,with Comparative Example 1 (regular tire) set equal to 100. A higherindex indicates better cavity resonance-reducing properties.

<Generation of Vibration (Vibration Test)>

The generation of vibration was evaluated as described above.

<Air Retention Test>

Air retention properties were evaluated as described above.

<Puncture-Repairing Properties (Sealing Performance)>

Puncture-repairing properties (sealing performance) were evaluated asdescribed above.

TABLE 4 Resonator Frequency (Hz) 220 Size (inner A₁ (width) 3.2diameter)/cm B₁ (length) 3.2 C₁ (height) 3.0 D (Diameter of opening areaS) 0.5 L (Tube length) 3.5

TABLE 5 First tire Example Example Example 21 22 23 Resonator LocationInner Inner Inner equatorial equatorial equatorial plane plane plane Onerow One row One row Number  50  10  4 (Total number, 220 Hz) Arrangementin tread Equal Equal Equal circumferential intervals intervals intervalsdirection Symmetry Symmetry Symmetry Material PP PP PP Sealant(with/without) with with with Subjective noise (Cavity resonance) 130110 103 Generation of vibration No No No Air retention properties 100100 100 Puncture-repairing properties 100 100 100

The self-sealing tires of Examples 21 to 23 (first pneumatic tires)including resonators exhibited sufficiently reduced tire cavityresonance (road noise). They also had excellent air retention propertiesand excellent puncture-repairing properties without generatingvibration.

REFERENCE SIGNS LIST

-   10 Tire-   11 Inner periphery of tire-   14 Tread portion-   15 Carcass-   16 Breaker-   17 Band-   20 Sealant-   21 Wider portion-   30 Nozzle-   31 Tip of nozzle-   40 Non-contact displacement sensor-   50 Rotary drive device-   60 Twin screw kneading extruder-   61 (61 a, 61 b, 61 c) Supply port-   62 Material feeder-   d, d₀, d₁, d₂ Distance between inner periphery of tire and tip of    nozzle-   300 Resonator-   301 Tube-   301 a Opening-   302 Cavity-   310, 320 Self-sealing tire-   311 Tire component (including innerliner)-   312, 323 Sealant layer-   313 a, 313 b Resonators tuned to the same frequency-   314 a, 314 b Resonators tuned to the same frequency-   321 Tread-   322 Circumferential longitudinal groove-   324 Resonator-   325 Lateral groove

1. A pneumatic tire, comprising at least one resonator on an innerperiphery of the tire, the resonator comprising a tube with an opening,and a cavity connected to the tube.
 2. The pneumatic tire according toclaim 1, wherein the inner periphery of the tire corresponds to a treadportion.
 3. The pneumatic tire according to claim 1, wherein theresonator is a Helmholtz-type resonator.
 4. The pneumatic tire accordingto claim 1, wherein the opening is provided to face an inside of thetire and/or to penetrate outside of the tire.
 5. The pneumatic tireaccording to claim 1, wherein the opening is provided to penetrate acircumferential longitudinal groove of the tire.
 6. The pneumatic tireaccording claim 1, wherein the pneumatic tire comprises the multipleresonators tuned to different frequencies.
 7. The pneumatic tireaccording to claim 1, wherein the resonators are circumferentiallyprovided at substantially equally spaced intervals.
 8. The pneumatictire according to claim 1, wherein the resonators tuned to the samefrequency are provided circumferentially symmetrically about an axis ofthe tire.
 9. The pneumatic tire according to claim 1, wherein the cavityof the resonator has no bottom surface, but a surface of a sealant layeris provided as a substitute for the bottom surface, and the opening isprovided to face an inside of the tire.
 10. The pneumatic tire accordingto claim 1, wherein the pneumatic tire comprises a sealant layer locatedradially inside an innerliner, and the resonator located radially insidethe sealant layer; the sealant layer is formed by continuously andspirally applying a generally string-shaped sealant to the innerperiphery of the tire; and the resonator is attached with the sealantapplied to the inner periphery of the tire.
 11. The pneumatic tireaccording to claim 1, wherein the sealant comprises a rubber componentincluding a butyl-based rubber, a liquid polymer, and an organicperoxide, the sealant comprises 1 to 30 parts by mass of an inorganicfiller relative to 100 parts by mass of the rubber component, and thesealant layer has a thickness of 1.0 to 10.0 mm and a width of 85% to115% of a width of a breaker of the tire.
 12. The pneumatic tireaccording to claim 1, wherein the sealant layer is formed bysequentially preparing a sealant by mixing raw materials including acrosslinking agent using a continuous kneader, and sequentially applyingthe sealant to the inner periphery of the tire.
 13. The pneumatic tireaccording to claim 12, wherein the sealant discharged from an outlet ofthe continuous kneader has a temperature of 70° C. to 150° C.
 14. Amethod for producing a pneumatic tire, the method comprising the step ofattaching the resonator.
 15. The method for producing a pneumatic tireaccording to claim 14, wherein the method comprises the steps of:continuously and spirally applying a generally string-shaped sealant toan inner periphery of a vulcanized tire; and attaching the resonatorafter the application of the sealant.
 16. The pneumatic tire accordingto claim 2, wherein the resonator is a Helmholtz-type resonator.
 17. Thepneumatic tire according to claim 2, wherein the opening is provided toface an inside of the tire and/or to penetrate outside of the tire. 18.The pneumatic tire according to claim 3, wherein the opening is providedto face an inside of the tire and/or to penetrate outside of the tire.19. The pneumatic tire according to claim 2, wherein the opening isprovided to penetrate a circumferential longitudinal groove of the tire.20. The pneumatic tire according to claim 3, wherein the opening isprovided to penetrate a circumferential longitudinal groove of the tire.